A keyboard you enjoy using will help your touch typing, lots of people do enjoy mechanical keyboards but other people prefer light scissor switch keyboards.
Personally I don't like the buckling spring system the unicomps use, but I do like other types of mechanical keyboards (particulaly those using Alps switches or copies).
If you're not sure what you like then why not start with a keyboard availible closer to home? You could get the Cherry G80-3000 in a UK layout from many shops in the UK. The G80-3000LSCGB is the most popular version as that has the clicky blue-stemmed switches.
EDIT: There's also
this one with a slightly different layout that you may prefer, but I don't know what type of mechanical switches it has (and some are unpopular) and it is more expensive. The last one someone on here got had Alps switches (which I like), but there was some uncertainty to how old the keyboard was so they may have changed it now.
Or if you're on a budget mechanical keyboards do come up on ebay for ten or twenty pounds fairly often, I generally keep an eye on there and post anything interesting here. Currently I think there's only the SGI AT101 which is supposed to be a very nice keyboard but is US layout and that particular one needs cleaning but there's bound to be something along within a month or two.
You could also ask in the marketplace and see if anyone here is willing to part with something with a UK layout.