Just a note on O2 recycle. I think there is some caveat that they take a certain percentage off for any scratches etc, which I think is why the price is a bit higher than Mazuma etc. Not 100% on that, but might be worth checking the T&C's carefully before sending it off!
Definitely worth looking here:
http://www.o2recycle.co.uk/termsandconditions.asp#damaged