co.uk domain .. i think it can be helpful for rank in UK Google... you need to find some uk sites and need to send them link exchange proposal... if you get some back links from UK domain sites... i sure you will get rank... Cheers!
I am in the Uk and have lots of sites on a US server. It dosn't make any difference where the server is. Like someone has already suggested, register your domain on google webmaster tools, go to settings and then set the Geographic target to UK. This will work.
Dont do that if u want to maintain your ranking for com Google.co.uk have different behavior then that of co.uk .. its something similar to co.in .. so I suggest you to have backlinks from some uk websites, Also try to list your business into google local this will help alot !! Have uk postal address on every page of your website !! and at the end .. links, links, links and links from uk based sites !!