Welcome JZD. A few years ago I put some thought into what I called gerribikes, i.e. bikes for geriatrics, on the assumption that I would not be young forever. After building some possible solutions, the first major principle I arrived at was low-step-through/over, same as you have. The second was surprising, to minimize unnecessary bending over the bike, which has a huge consequential trail of corollaries. The third, probably not applicable to a practiced cyclist like you (my guinea pigs were people in their sixties cycling for the first time, because the extreme case throws up necessary lessons faster), was to be able to put at least one foot on the ground while seated on the bike. I didn't even bother to test posture on the bike: I knew I would like to sit upright, in no kind of a racy posture.
Thorn usually manages to fit everyone, and we had some short ladies here who were notably well-fitted, so my tips are not about fitting but about outfitting your bike so that twenty years from now you will still be able to use it with pleasure.
The Rohloff is good. It has a huge range of gearing. I has low service requirements. It works well with the Hebie Chainglider, which further reduces service and adjustment events. You need to specify your chainring to be one of those for which Hebie has a Chainglider front end available which works with the Rohloff-specific Chainglider rear end. Off the top of my head, that's 38, 42 and 44 teeth. Your sprocket to work with these chainrings can be 15, 16 and 17 teeth, but there is an advantage in chain life and less service with the even-even choice of a 16T sprocket. (That one is also free with the Rohloff.) Furthermore, you need to specify a chainring that isn't too thick for the Chainglider; Thorn's own excellent chainring is too thick; a good choice is Surly's stainless steel chainring.
You'll already have your own ideas on tyres, but note that the Raven can take 55mm/2.15in Schwalbe Big Apples, low pressure balloons of great comfort and yet very low rolling resistance and superior speed. I'm a big fan of the Big Apples. Don't take the Marathon Plus as it's harsh, but other Marathon touring versions have fans here. Get the widest mudguards Thorn have in stock, P65s if they fit, because this leaves your tyre choice open to tailoring for specific types of riding/places to ride that maybe you cannot now foresee.
A useful lock that doesn't require bending over the bike is the n'lock, which is a high-quality Swiss stem that works like a car's steering lock. Last time I looked, Thorn had some base models in stock, but what you want is the adjustable model, with the facility to take the cable lock as well. There are two cables, one inside a handlebar, with a variety of bar shapes available, one a much longer loose cable with a loop at one end. I live in a low-crime area (where all the low-lifes know I react violently to being stolen from) so I just lock the steering column of my bike, without the cable, in any place where I can see it through a window. When I can't see it, I lock it to a rail or a lamppost or a street sign with the handlebar cable. If there are suspicious characters around, I lock the rear wheel around a pole with the long cable to the n'lock. For going to the wicked, thieving city, and riding among carelessly driven Range Rovers, I have an Abus Granit-X U-lock clipped just under my seat where I can reach it instantly if a carelessly-driven Range-Rover comes within reach. It can also be used to fix the rear wheel and frame immovably to a lamppost or tree, though I rarely bother.
I don't need to tell someone who lives in Sweden to specify a hub dynamo and good front and rear lamps. The sporting Shimano hub dynamos are in my opinion as good as the SON (I have both) for almost all applications, but on a bike to see you out you may as well specify the SON. The BUMM Toplight Line Plus is currently considered the best generally available rear lamp and as a bonus it is, by BUMM standards, not too grossly overpriced for an ugly piece of plastic. BUMM's IQ lamps are held in high regard here; the CYO is especially valued for its light output. You should also have reflectors front and rear.
A Brooks leather saddle of course, unless you're bringing your own well-shaped one with you from your previous bike. People here like the Ergon grips which are an aesthetic mismatch to a Brooks saddle, but horses for courses. You can get Brooks leather grips to match a Brooks saddle. I use Brook's edge-on leather ring grips that match my saddle and they are superb.
You don't say what sort of pedals you use, but if you like old-fashioned rubber block pedals, SJS stocks the VP-191, which is a silken-smooth sealed bearing pedal; I have it on all my bikes. It is also pretty reasonably priced for such a long-lived pedal, it's only fault being that it is not very wide, which shouldn't bother you.
By the way, though I don't ride a Thorn (I'm an artist: a welded bike rubs me wrong from thirty paces away), I hang out here because Andy Blance, the Thorn designer, always knows all the best components, no boutique rubbish, and when what he chooses doesn't suit me, one of the posters will know.
