Check it out via Google. see what current UKonline users think and how they are regarded for service - and backup - but then examine the small print to see what, if any download limits there are. Not much cop going at the speed of light if you use your limit in two hours.
You get what you pay for - usually....
Conan
PS re: the BT email address. Have you thought about getting a cheapo domain, ie
[email protected]? Any email will be reirected to it so you have no worry if you change ISPs - but I would prewarn people a little in advance.