Warning: link to site with potential scam affilliations ahead. The "Free" iPods on offer at ipods.freepay.com aren't as free as they'd like to make out. But you can get one for a lot less outlay than it'd otherwise cost if you're careful.
Basically you have to sign up for some additional service (along the lines of a rental service subscription, or a dvd club type service). You will have to spend, but you can qualify by spending under 100 quid, which is a damn site less than you'd pay for the iPod.
Some of the promotions have a distinct scam-like whiff, so be careful to read the small print.