Your question is not clear -
I'll ask the question - "Which domains are useful for selling into the UK?"
My answer -
The economical domains to use are .co.uk, .org.uk, .com and .net . You will find these are the cheapest Top Level Domains (TLDs) to register, and that they will index easily on the search engines. If .com / .net are hosted on UK servers, there is no problem targetting your audience.
There are other Top Level domains that can rank highly with the search engines with content in English, like .de and .ie . These cost more money to register, but it can be worth the extra money to get the name you want.
Secondary domains like .biz and .uk.com can give reasonable results, but they are expensive to register, and largely ignored by most people. As far as I can see, that will be the case until they run out of people willing to pay a premium price for the name they want. Then prices will drop ...
Andy Pandy's coming to play, tra-la-la-lala-la