George,
There are a lot of interesting places to see between London and Edinburgh, and some great scenery.
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If I wanted to shorten the journey I would take a train to Cambridge from London and start riding from there.

UK has lots of shops.  Petrol stations are usually open and sell food so no need to carry too much.  If you need something you will probably be able to buy it.

Google maps tells me that London to Cambridge is roughly 60 miles (sorry, I am still thinking miles, not km), that is a semi-long day on a bike.  I think I will pass on the train, as the train adds enough complications as as luggage, etc.  but thanks for the suggestion.  Being in USA, I am not used to convenient train travel, as our network of trains is quite poor.  So, if I planned to do very much train travel, I would have to spend a lot of time on education.

Perhaps your petrol stations have more normal foods than USA petrol stations have, ours rarely have much nutritious foods to eat.  I have diabetes, I have to limit my carbohydrates and that means minimizing overly processed convenient foods.  On bike tours, I often stop at restaurants when I see them so that I can eat nutritious food.  And after my Iceland tour, my doctor diagnosed a severe protein deficiency, so I have to make sure I am getting plenty of protein every day.  So, I anticipate looking for well stocked grocery stores.  A few days ago I put together a list of your main grocery stores and their internet sites so I can look for locations of them when I need to.  And my GPS is usually pretty good at finding grocery stores.  I usually carry several 20 gram protein bars so that I can have one a day for the extra protein.

Attached photos, two of my suppers on my last bike tour, a canned soup and a canned stew.  My stove can use both the long skinny butane cartridges like in those photos or shorter wider cartridges that you thread the stove onto, that threaded type canister is in the third photo.  I did not plan to bring a stove that goes on the unthreaded French canisters, but if those are common I could bring that stove along too.  Fourth photo is that type of stove and the French canister.  So warn me now if I need to also bring the French stove as that was not in my plans.

My last bike tour was a bit over two weeks, I rode a distance of 662 miles, or a bit over 1,000 km.  But that was mostly on reasonably flat ground, and I plan to ride shorter daily distances on this trip.  This trip as planned is about 50 percent longer, but I can easily adjust the latter routing to shorten it if I have to.  And thanks for the many suggestions here for Scotland routing, I plan to completely change my Scotland routing.

East Coast:
- Cambridge
- Lincoln
- York
- North York Moors
- Durham
- Newcastle
- Northumberland coast

That's a good itinerary for a first tour of the UK. So is Andy's west coast ride, especially the Lake District if you're a city dweller.

But a second tour could specialize. For instance one could visit the smaller cities with cathedrals. (Actually they're towns, jumped up to being formally cities because they have a cathedral, which on the whole makes them better places to cycle in as many of them have narrow streets e.) Academics and other friends from all over the world came to stay with us in Cambridge and a universal demand, after tours of Cambridge colleges, and a scull on the river, was for a half-day trip to Ely Cathedral, which accounts for how many people have photos of themselves in the Bishop's Door at the Cathedral. Pronounced not E-lie but E-lih as in 'lick'.

Or a tour of fishing ports like Whitby.

If I wanted to shorten the journey I would take a train to Cambridge from London and start riding from there.

Absolutely. London, except the City (meaning the financial district, like Wall Street), which is architecturally interesting, and the bicycle path beside the Thames, is dangerous for cyclists. Cambridge is a good place to start cycling without being stressed out for no good reason.

Hi folks. I've been a bit slow to catch up on this thread.

If any of you pass through or near Aberdeen, please contact me for support or accommodation.
Aberdeen has the ferry/ship to Orkney/Shetland. I have been to both several times and can highly recommend them.

A few years ago I rode from the top of Scotland/Shetland, down to the Southern most tip, Mull of Galloway, via the Outer Hebrides and islands.
So can offer advice/thoughts of the West side of Scotland.

Best wishes

Have you considered using the train for both forward and return journeys to London and leaving the bike somewhere secure in Edinburgh? In my opinion the time saved cycling between London and Edinburgh would be better spent exploring Scotland in more detail, it would also address earlier comments about bike security in London.

Indeed. There is, for example the north western half of the NC500 https://www.northcoast500.com/ which I confess I've driven but not cycled but have seen touring cyclists on it. It's probably best tackled clockwise as the prevailing wind is from the SW. Probably the biggest hazard is tourists in campervans. There's potential for a good circuit comprising Edinburgh - Glasgow - Fort William - up the west side - along part of the north - south to Lairg - Inverness - Edinburgh. This misses out JOG which, to be honest, doesn't have much to offer except being one end of the LEJOG (Dunnet head is further north).

Hi, George

I’ve thought of a few things that may help with your planning. in no particular order, here they are.
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I planned to make the reservation for the airline, three hostel stays (upon arrival, in London, and just before my flight home), and train in the next week or so.  The train from Edinburgh to London is the only train I anticipated. 

I need to do a bike ride with my mirror to see if I like it, but tentatively it should work.  But it does vibrate slightly.  First photo.  I think I should have the mirror on the right side, for one thing that will remind me to ride on the other side of the road.

My helmet mirror can only go on the left side, it has a clamp that clamps onto my visor, second photo, the clamp is at an angle that puts makes it specific to only the left side. 

I am not going to go out of the way to save a few (almost said bucks for USD) quid (for GBP) if I am only riding one train ride.  But thanks for the suggestion.  A month and a half means that the costs will add up, but by mostly camping and hosteling, and most of my food would be cooked in a campsite, the total trip cost should be quite reasonable for that amount of time.

I did my Iceland trip a decade ago, about five weeks long.  That same year my sister did a two week guided group tour of several countries in Europe.  Afterwards I told her she really screwed up, her trip was only 40 percent as long, but cost twice as much as my trip.  She could have done two of my trips for the price she paid.

Third photo.  This was either Nova Scotia or PEI (Canada), the mosquitos were waiting for me to open the door for them in the morning to let them in for breakfast. 

I mentioned a few times that I have sprayed some of my clothing with Permethrin.  One problem with bugs and biking is that most bike jerseys are mesh and all those tiny little holes are there just so that bugs can easily bit you the moment they land on you.  Hopefully, but treating some of my clothing, that should help.

I am used to camping where there are a lot of bugs.  I am originally from Minnesota (USA).  And as a Minnesotan, I have some immunity to mosquitos.  In Minnesota, the mosquitos are quite large.  If they taste a baby human and the baby tastes good, they carry the baby off to eat later.  But if they taste a baby that tastes bad, they leave them behind.  Thus, after several generations, the humans don't taste very good to mosquitos.