.com is american
.co.uk is british
so for locality reasons your better of going .co.uk for SEO reasons, and ensure your website hosts, host your website on a uk ip address.
If your a national, multi national or international company then you go .com
That one is a double edged sword. For Google rankings .co.uk is better,.. BUT,.. someone typing a web address from memory will nearly always type .com first,...
Best to have both URL's if possible.