Andy_Langton - 8:58 pm on Mar 26, 2013 (gmt 0)
If you redirect US visitors from .co.uk somewhere else, you won't get any crawling of those URLs (or any indexing) and thus no rankings for UK search.
Using ccTLDs like .co.uk is the right approach (and a much better approach than subdirectories). The current geo-targeting process is wrong.
If someone directly navigates to a .co.uk domain, they should see UK content and should not be redirected. Use a .us or .com if you want US/worldwide targeting, and redirect (for instance) UK visitors from the .com to a .co.uk.
Search engine infrastructure is US-centric, basically, so you cannot get geo-redirects to work any other way.