O2 don't compete on price. I was told this by the sales rep recently, they think they're superior and don't give a s.. about certain customers, ahem. O well, to ORANGE i went.. and a good thing it was as the Tmob merge means better signal for me, soon.
O2 are growing nonetheless, home phone/broadband is their next big move and the quality of their infrastructure should remain strong. I guess you pay for quality with O2. Despite their careless customer care division (oh the irony), their network service is probably the best out there.