from www.mobiles.co.uk (owned by carphone warehouse). Multiple pesky redemptions needed. If you don't send off the relevant bills it costs £33/month.
Unlimited minutes, unlimited texts, 1gb data.
Things to check before you buy -
(i) 3g or 4g
(ii) check whether it's a refurb - it doesn't say it is, but O2 have been flogging a number of refurbs lately and maybe this site doesn't declare it...
EDIT: and it is a refurb, so pls ignore!