Hi Marcus.
As stated in a previous post
www.milweb.net is a good place to start looking in the U.K. or try everyone's favorite auction site.
The main thing with these trucks is they need to be maintained to a good standard, as they have a single circuit brake system, parts are not to bad to source from the UK, I tend to get mine from Europe and the U.S.
Tyres are quite hard to get hold of in the U.K but not imposible. These trucks are a bit of a handfull on British roads with a large turning circle and no power steering.
Storage can also be a problem, as your neighbours are probably not going to be happy if you park it on your drive/street, if you get a 'C' Turbo model they are very loud and you will need hearing protection in the cab.
After all that is said they are great fun to own and drive, also you have started off on the right foot by coming onto steelsoldiers.com there are many people on here with a great deal of knowledge about these trucks who can help you.
Good luck with your search.