My site is a .com site, hosted in the UK.

For a basket of keywords and phrases, I have good rankings on Google.com but not on Google.co.uk.
However, I have good rankings on Yahoo.co.uk but not on Yahoo.com

I would have thought that if I have a location problem I would, for example, have good rankings on Google.com and Yahoo.com but not on Google.co.uk and Yahoo.co.uk (or visa versa) - but not the .com on one search engine and the .co.uk on the other search engine.

Does this make sense?

Any ideas on how I can figure out why this is....and what I can do about getting better rankings on Yahoo.com and Google.co.uk?

Thanks
SEO Idiot

How far-fetched would it be to suggest that Yahoo might actually be better than Google in some cases?

FYI: I know Google recommends getting the .co.uk domain for such country-specific sites and purposes. Any reason you are using the .com if you really care more about the UK traffic and engines?