Don't know if you've come across this but it could be a useful site. [url]http://whocallsme.com/[/url]
I had a few calls yesterday to my mobile from an 0800 number, I didn't recognise it so ignored it on the basis if it was genuine they'd leave a message. They didn't so I Google'd the number and it pointed me at the above website. If you get any calls and don't know the number you can see if you can find out who it is who's pestering you without having to call them back, some are at premium rates.
Mine turned out to be Norwich Union. When I bought my car the 7 day driveaway insurance was with them so no doubt they are trying to call me to flog me a policy now. Bloody cold calling barstewards! They never leave a message so it can’t be anything to do with the 7 day policy.
Anyhoo just thought I'd let you know, a site worth bookmarking. As an example this is the number that was calling me 08004046092, so if you stick that in you'll see how it works.