Steven,
What problem are you trying to solve for here? Are you buying so much wine from wineries directly that you either cannot transport it to the UK yourself, or go through the customs process?
In my (fairly limited) experience, it's often cheaper to buy wine from UK retailers / importers, than it is to buy from a cellar door anyway. If they don't have a UK stockist, it's possible that the wine you're looking for will be stocked by someone who will at least deliver to the UK for you. In any case, try Wine-Searcher.
I think a little more information might help...