Sailing; either dinghy or keel boats (yachts), can be expensive, it all depends on how big the hull and sails are, and certainly can be exciting.

Targa Rallying: Very limited modifications, cheap entries, competition is off the highways, tends to suit smaller, nimble cars (K11 Micra, MG ZR/Rover 214, Toyotas etc), so could be seen as recycling old cars

It is based on the vehicle, not the registration mark. We have a cherished number and if you check it only shows the details for the current vehicle. I did get an MOT reminder message for a vehicle I didn’t recognise; checked the history and it was our previous Discovery which had reverted back to its original VRM when we traded it in, then had another cherished number assigned to it.

I find Galibier sizing charts pretty accurate. Alternatively, with them a call and I’m sure they will advise.

Planet X London Road frame might be an option;
Room for 43mm tyres, discs, aluminium

I’ve used mine for 100km Audax (with 32mm road tyres), currently running 43mm Rock ‘N’ road tyres, on 700c rims, could run 650c apparently

As others have suggested C1/107/Aygo are cheap, basic and functional.
Hyundai i10 is another good call
Any Toyota
Skoda Fabia
Nissan Note
Honda Jazz
Fiat Panda
Avoid Vauxhall Corsa (rotten subframes)

Have a look at Galibier

Another vote for the Dualit Classic. They’re basically clockwork/manual operation, look good, easy to use. HAd ours for about 20 years.

If you have a COSTCO card ( or are elligible for one), try there. I’m sure that what we saved on the toaster was more than what the years membership fee was.

singletrackworld.com/forum/topic/bike-clothing-poor-value-and-poor-design/page/2/#post-12088516

Have a look at Lusso or Galibier.cc for unpadded bibs

First thing to consider is what size of van; anything significantly bigger (longer/wider) than something like a VW van or similar is going to be a nightmare on some of the route. There are many parts that are single track with passing places, hairpins and steeps, especially the pass to Applecross where anything large will probably get stuck or at least block the road at some point. If you are not used to driving a vehicle of that size you will suffer.

Why not stick with your original plan of using B&Bs? You support local economy, get to meet the locals (or incomers), get local tips and advice, have a relaxing time. There’s some great B&Bs and small family run hotels. I can strongly recommend The Melvich Hotel as a place to stay, superb views and food. I’d also take a day out to do a trip to Orkney; you can travel as a foot passenger on the ferry to meetup with the tour bus and get a tour of the islands. Incredible views and history. There was another nice hotel on Loch Shin worth detouring off the NC500 for.

For some balance, I’ve just managed to secure a Laufey H30. Only collected it this week, so yet to ride it. My short list was the same as the OP, Merida Big Trail of Laufey. Supply made the decision for me.
At 6’1″ I went for L in the Laufey, but was looking for XL in the Merida.