They're both pretty terrible but for different reasons, OP didn't even acknowledge there was a problem with the screen, twice, but they did turnaround both times in less than a week. Also, their communication is terrible and very impersonal/generic which I guess is to be somewhat expected from a large company. Regardless, the phone should have never left the factory in the state it was in, OP's standards are too low or their QC department is crap.
I never actually got O2 to acknowledge the fault beyond the lady in the shop seeing it, the first time I sent it off they sent it straight back saying the phone wasn't purchased at O2, I had the receipt in my wallet so the phone was sent back 10mins after I had received it and that's the point at which it was lost, it seems.