Incidentally, O2 are running what I consider to be close to a scam.
I bought my phone, a Galaxy, on their finance plan. My monthly charge before financing £26.....After a year, I was flush with funds and bought the rest of the plan out. First of all, they tried billing me for insurance - not their decision and their local rep went ballistic at the HO. More appalling though was that, for exactly the same terms of usage as to minutes/bytes etc, my monthly dropped from £26 to £14.75 - so beware, on top of the financing charge they are skimming more than a tenner per month off you.