Buying a name in ccTLD that is not trademarked

Establish prior use in a niche with your domain by developing it. Try to avoid the same topic as the com if it is developed, or make it appear different. Use ads carefully.

andyr

If you develop your site in a non-descriptive way you can develop common law tm rights in the US, at least. Then if they try to enter the same market you are in, then you will have a case (no guarantee). If they develop first, and you try to enter their market with the same name, then they will have a case. Nothing is guaranteed but develop early and fast and you will significantly improve your odds of being able to udrp them should they enter the same market (unless you use it for the descriptive meaning of the phrase, then you can't claim tm rights in most cases).

USPTO = USA
.CO.UK = UK

Check the relevant UK trademarks etc, but generally speaking unless you use your .UK domain to abuse other peoples rights you ought to be fine