Hi Dave,
I cannot agree with Flibb about what he says about 90s or 110s for long distance.
True, the 90 does bounce around a little when on the road, but it is still comfortable, and excellent off road. It would be difficult to beat it. The 110, however does not bounce around due to the extra weight and I think it is brilliant for long distances. I have travelled extensively through Europe many times and I don't find any discomfort. Obviously a later model Range Rover would be more comfortable, but for £5000, I'm not sure what you'll get.
I do agree about the 101, however. These are amazing vehicles, but very expensive to run. A V8 diesel transplant would be nice.
I think the most practical option would be a 110. The engine should be either 200 or 300 Tdi. These are both reliable engines and when cruising will give you 30 mpg. There are some 300 Tdis that had problems with their timing belts and had to be modified, so be careful. With either of the engines, you must make sure you find out when the last cam belt change was. If you're not sure, change it. They say every 72,000 for the 200 and every 60,000 for the 300, but I do mine every 35,000 miles.
Some of them have covered many miles and might put you off, but most of them will have done close to 100,000. Mine is on double that and I intend to go to 500,000!(engine only), other parts will have to be renewed.
The rear seats in the 110 don't give you much leg room, but there is so much potential to build it to your spec.
The things to look out for are rust on the bulk head, chassis and rear cross member. You can get repair parts but you shouldn't need them if the owner has looked after the vehicle. A lot of the handling problems are due to nothing but worn trackrod ends and worn bushes which are minor jobs and transform the feel when repaired.
You should be able to get a good ex Army Land Rover for £3500 but it will only be 2.5 diesel with no turbo. A good engine but a bit slow. An Army Land Rover, though, would make an excellent base vehicle for which to create your own multi purpose utility wagon.
If you don't know it, then this is a good place to gain any information :
www.difflock.com
Good luck in your search and I hope you enjoy many miles with your 110.
Cheers, Julian.