neat, I would be interested to hear how it goes, how it is getting out of Cardiff and up the coast etc etc.

I havent ridden in Wales, but in car and on foot, I can assure you that it can be bonkers hilly, with 20% climbs fairly common so keep this in mind and keep your load down to a minimum. Not to mention gearing, I dont recall the gearing of the stock LHT, probably a 26 granny and a 32 or 34 rear, so probably around 21 gear inches. I'd recommend a couple of things, 1- to be sure to ride with stuff on your bike as much as you can in hills if you can (you could live in Texas or Florida) and
2- to ask some route advice over on the Brit touring forums, I think it is CTC? Someone else may know, but I figure thats what I would do when and if I plan a trip by bike over there, just to get local advice on roads and such.

Your est. 50mi. 80km per day is probably reasonable, but do be aware that constant ups and downs, especially steep ones, will wear you out, so definitely getting local riding advice for a bike that weighs 65lbs or more would be good to have a better idea of realistic distances given the climbing.

I would even hazard to say that in this terrain, lower gearing would be a bonus.
With the internet, its possible to read about or to see actual routes and grades, so at least this summer you can hopefully ride on similar hills, because in steep stuff, every 5lbs of stuff makes a heck of a diff, and you will be able to see how the stock gearing works for you.
As always, being prepared physically means a more enjoyable trip, pure and simple, and lessens the chance of possible knee issues or whatever that can screw a trip up, especially one you've paid a fair amount of money to fly to.
cheers

PS--Oops, just quickly looked at your Touring Blog link, and I see you are not American, and do have a lot of touring experience, so sorry for the simplistic blah blah.
cheers again.

PPS-have to laugh, actually read the beginning of your pages and so saw that you are a Yank, from Co. Well, at least you will have hills to ride on!
And I looked up the CTC forums and sure enough, you have already thought of that. Shall bookmark the discussion for future use.