Hey dude!
Umm well don't get a cheap one lol, like the Dean thing! Eugh
The most popular EUB is probably the NS Design Upright, can be seen in most of the Bass orientated shops in London, Cellar, Gallery, Centre etc.
The Bass Gallery in Camden usually carrys a few other makes, some second hand etc.
Then theres the few Custom builders in the UK, Mo Clifton is in Blackheath in london and John Shuker is in Sheffield. Theres a few other builders to.
I personally play a Shuker 36" scale EUB, and a good friend of mine has the Clifton Mini Mo, both cheaper then the NS Design, but you have to wait until they're built to try them obviously. You're more then welcome to try my Shuker if you want a trip out to south Bucks.
Hope this helps
Si