hmm.. i don't know much about the uk, but I really wouldn't worry about currency fluctuations. If you buy hosting for say 2 years you only pay for currency conversion once at first payment.
If you don't mind this, take a look at site5.com. they currently have a promotion for unlimited bandwith, space , etc for $8 US a month.
I use them for all my sites and they're great, they essentially virtual host mutiple sites on a server, so you are getting most of a dedicated server's features - unique shell, etc.