^ +1!
Location is down to your ip address. The gay-boys in the dating ads that's from having analysed your previously stated preferences I suppose [er

].
[Ahem] More seriously. The dating pics are the only ad I get up, but I connect directly to the local ISP. However if you are using a proxy-ip, to connect as if you are in the UK, usually used to circumvent SGn etc web-censorship (and BBC iPlayer blocking etc), then IME it is common for such a proxy network to put local ads from the proxies location into your header as a 'banner'
If it's getting to you, you can look into installing a piece of software called an ad-blocker (web-search it). The dating ads to the right don't actually bother me; however having a scrolling sidebar AND header can become such a distraction it become something of a PITA.