Firstly, I assume that you're actually using the UK option (from the arrowhead thingy at the right of the search box), rather than just clicking on the magnifying glass (or hitting 'Enter').
If you are then there might not be anything that you can do about it as many international websites are deliberately designed to shout "Yes, we're located in the UK . . . and France . . . and Germany . . . and Australia . . . and India . . . etc, etc" to search engines, in the hope that they'll get at least a small amount of extra trade for their websites. (Further, the firms that companies employ to push their websites up search rankings often get paid by the number of hits that their clients' sites receive; they couldn't care less that you're clicking through to a completely useless site as long as they get paid for you doing so!).
So you'll never get solely UK results from any search engine. Indeed, because of the tricks I've outlined above, the ability of search engines to restrict results to a single country seems to be getting worse and worse.
Sorry!