Download and install the AdSense Preview Tool from https://www.google.com/adsense/previewtool
Now go back to Gmail, right click on the page and select "Google AdSense Preview Tool". Make sure you select UK under the Options link. Now compare the Gmail ads with the ads displayed by the Preview tool.
Are they identical?
>>> however NONE are from the UK.
Now are you absolutely sure that you are in UK? Sometimes, you will never know where you are after a few pegs.
vibgyor79, no I'm saying that if I try to visit google.com, I get redirected to google.ca and get served results and ads for Canada. For Gmail, there is no checking of IP addresses etc. to determine location, and the service is just in US English - so I would assume that there is no geo-targeting of ads either for that reason.
That's not to say it won't happen before launch - as things are still in beta, that feature may simply not have been enabled yet (along with other languages for the interface and the rest of it).