The best solution is perhaps to
use both a dot.com and .co.uk domain where the first is hosted in the USA and the second in UK.
Related WPW threads:
Google UK results diverge
Does G treat .de and .com the same
Trying to work out foreign googles
Matt Cutts:
More SEO Answers on Video
If you need more, try:
"host location" site:www dot webmasterworld dot com 37 Hits.