Plenty of good info to keep you interested, I hope it isn't overload!  Just a couple of points to add if you hadn't already realised.
Camping off site is permitted in Scotland as long as you follow the guidance:
https://www.nature.scot/sites/default/files/2017-08/SOAC%20-%20Publication%202017%20-%20Camping%20in%20Scotland.pdf
Not so in England, though there's plenty of opportunity to go unnoticed if you arrive late and leave early.
There's a few bus services in Scotland that take bikes, I don't know the details, maybe someone else does.
I think everyone, including me, has their favorite Scottish island, I haven't been to them all, but have enjoyed all those I have.  Enjoyed Skye less than the others, there's a clear correlation between ease of access and wilderness.  Mull has an advantage that it can easily be incorporated into a circular route, arriving back on the mainland a long way from where you left it. 

When I was in the Highlands in September '24, several of the campsites had "full" signs, but that was for the RVs and caravans (trailers). They all had room for a cycle tourist.

If you are enjoying Scotland so much that you want to keep riding, or if you need to return quickly to Edinburgh, keep in mind that City Link and Ember busses take one or two bikes, depending  on the route. City Link supply a stretchy bag to cover the bike, and it and the panniers go in the baggage hold. Don't know the procedure with Ember as I didn't use them.

Ember didn't require covers for bikes on the 5 times I've used them.
Stagecoach can an be fussy at times.

Yes, to camping sites letting cyclists with a tent into ' full' sites. It certainly happened to me north of Ullapool

Thanks, especially for the warning that a lot of tourists could be there in June.  Thus, I should plan to make reservations at the hostels I plan to stay at.  I usually have made reservations for the hostels I use at the start end end of a trip, but not the ones I stay at in between.  And I almost never make reservations at campgrounds.  I will think a bit more ahead on this trip, and may make reservations when I have a good idea of where I am going each day. 

I put a lot of the hostels in my GPS, I have been thinking I might spend more time in hostels in Scotland than in campgrounds.

I think I will do a lot of grocery shopping at Sainsbury in England, then in Scotland after Glassgow shop at Aldi, Coop, Morrison, Lidl.  I put a lot of the grocery stores into my GPS.  The location of the store, meaning how much additional pedaling I have to do to get to it, is much more important to me than the price they charge.  Once I leave Glasgow and before I get to Inverness, the communities will be small so I put everything into my GPS that I thought I might have to look for later.

I only work on my mapping and routing when I plan to spend some hours doing that, I use a vintage discontinued Garmin product (Mapsource) for that.  And it does not run on my Windows 11 computer, so I have to switch computers, which means a lot of unplugging and plugging in cables to use my older computer for that.  Yesterday I was looking at the map of the England portion of my route, decided to add more campgrounds to the map.  And decided to go from London to Glasgow direct instead of via Edinburgh.  Laid out a route for nine days between London and Glasgow.  But might take a zero day or two if I do not like the wind or weather.  Once I get to Glasgow, I have several options mapped out depending on how much distance I want to do for the rest of my trip.  When I get near the end of a trip, I have to start calculating where I want at the end of each day to make sure I get to my flight on time.

I took another look at climate data.  Decided to only bring long sleeve shirts and bike jerseys.  Bike pants will be long pants that have zip off legs.  I think I will bring the same type of clothing that I used in Iceland, that worked very well.  I might get a bit warm in the southern part of England, but I would rather not carry around warm weather clothing that I only used for a couple days.  I can roll up long sleeves when it gets too warm.

I still have a bit over five weeks, so that gives me some time to get in shape for this.

George,
Insurance.  With the uncertain state of the world and the (hopefully slim) chance for example that America might invade Greenland or Canada or some other place I would make sure that your policy covers flight cancellations. ...

Trying to read that stuff confuses me greatly.  I think I will stay both ignorant and trusting.  But thank you for your concern.  I have had flights canceled before but the airline was always pretty good getting that fixed.

That said, my 2019 bike tour, the airline and Expedia (the on line travel agent I used) got their wires crossed with the disruption of all of the 737 Max planes being grounded.  I could not figure out what was going on at the website, so I just made sure I was at the airport on time to get home.  The attached photo is the three ticketing agents in Halifax NS, Canada trying to figure out what was going on.  When I heard one of the travel agents say to another one, "another Expedia itinerary", that sounded grim.  Bottom line was that I was supposed to get on a plane in Montreal, fly to Chicago, then get on a plane in Halifax and fly to Montreal.  In other words they got my two connecting flights in the wrong order.  But Air Canada got me onto a couple flights and it worked out ok.

American Airlines is one of the three biggest airlines in USA, if they start stranding passengers, their stock would sink badly.  And the compensation of the corporate big shots are in part based on their stock price, so they will do everything that they can to limit any such occurrences.

If suddenly I am stranded in UK because all flights are canceled, I would rather be stranded in UK than a lot of other places.  I can pay my credit cards on line.  I am retired, so no employer to return too.  I have diabetes.  After four extra days I would run out of meds, but missing those meds would not be life threatening, I would probably would have higher blood sugar after a week, but not life threatening, I do not take insulin.

I am more worried that a shortage of jet fuel would cause a disruption in scheduling my flight back to USA from UK than I am of all flights being grounded for a period of time.

If suddenly I was stuck in UK because of an invasion of Greenland, I think most insurance companies have clauses that allow them to deny claims in case of war.  I would be surprised if they don't.  I did not vote for the moron in the White House, he has the self control of a toddler.  If any of you have read any of the columns by Martin Wolf in the Financial Times, I fully concur with everything that Mr Wolf says on that topic.  If I say any more, I suspect Dan will have to scold me for saying too much on that topic on this forum, so I won't.

I hope your extended stay in Sri Lanka was not as bad as I can imagine it was.

***

I have had two foreign bike tours where I planned to buy a local sim card, but never got around to it.  In those cases I always managed to do everything I wanted to do where I had wifi, including two times where I called my credit card companies using Google Voice on wifi to ask why my card stopped working.  Yes, I can make phone calls where I have wifi as long as I am in a country where Google exists.  I do not need any special app for that.

This trip I decided to make better plans to get a sim card, thus it is higher on my priority list.  At times it was inconvenient to search out wifi on those past trips.

Thanks for your comments.

RonS, Thanks.  My phone does not use ESIM.  Since I have never put a second sim card in my phone, I think it best to go to the store in case I need help in having two sim cards in my phone at the same time.  Maybe I should get 100 GBP from the ATM in cash then?  My only indoor lodging would be at hostels, I am sure that the biggest bill would be much less than 100.  Tipping, sounds like 7 percent when warranted works.

Matt2matt2002, thanks.  If I do Arran, that would be roughly mid trip, I would have time to cut distance off of my trip later if I got stranded there a few days.  That is why I laid out so many route options, the difference between the longest and shortest is about 200 miles.  But unfortunately Arran would not have cell service, so I could see that as a problem if a ferry was not operating.  I bought a travel insurance plan, it only covers emergency medical costs.  My regular health insurance also covers emergency medical costs.  Any other costs not deemed to be emergency would be up to me.  If I have a total medical disaster, my travel insurance covers costs to get me back to USA.  Wild Haggis, thanks for the humor.  Is it true that (pasted): The unicorn is our national animal.

JohnR, thanks.  I asked 1p Mobile if they could mail a sim card to me in USA, a few days ago they said they only mail to a UK address.  And they said all sim card sales are through the mail, none sold in stores.  I do not mind paying the EE price for two months of use.  For the three hostel reservations and airline reservation that I have already made, the tab is up to a bit over $2500 USD (~1900 GBP).  I am a frugal person by nature, but I do not mind on vacation spending a bit here and there to simplify things.  The coverage maps I looked at tell me that I only want an EE network card, not one of the others.  My mapped route options all should have good EE coverage, except Isle of Arran and some of the mainland north of there.

Regarding phone use:  I plan predominantly to check weather forecasts twice a day, morning and night.  And a bit of news back home for a few minutes each day.  And likely a phone call to my sister every few days to let her know that I am still alive.  If the sim card comes with phone calling option, I doubt that I would ever use it.  For my calls to USA, those would be using Voice Over Internet (VOIP) with Google, which I have used over the years from Continental Europe, Iceland, and Canada to call to USA without difficulty.  I also used that VOIP to make some of my hostel reservations in UK for this trip at a cost of only one or two cents ($0.01 or $0.02 USD per minute) which is cheap enough that I will not bother learning how to use a local phone number, if issued one.

In USA it is possible to buy a data only sim card, they are sold for use in tablets, etc.  Does not come with a phone number.  I was looking for that to use in UK, but it appears that is not an option in UK.  With a data only sim card, I can use VOIP with Google to make phone calls.  Google Voice is what that VOIP plan is called, it is available in USA but I think it is not available in UK. When I got my Google Voice account 15 years ago, it was only available in USA.

I plan to respond to messages once a day.  Thanks everyone.

It is a good thing I am retired, I have put a lot of time and effort to lay out these routing options, with campsites and hostels to stay at, grocery stores to make sure I do not starve, etc.  If I was still working, I would have had trouble finding the time to plan this trip.

One more question, is the "Sainsbury's Blended Scotch Whisky" or the Aldi "Highland Earl - The Special Reserve Blended Scotch Whisky" any good?  The price looks right for both options.  That looks like a good place to make some savings to pay for a better sim card.