This problem is NOT only in London.
Here in portsmouth the problems of 2G data Access and 3G Data access are all too common.
my friends and I are nearly ALL on O2 a few have iphone a couple with XDA's and a fair few with N95's and other handsets ..
we ALL have problems with data. and we ALL have problems with Failed calls where if you ring out .. nothing .. the timer on ya phone starts counting but noone there.
or the other way, you answer a call and there's noone there.
voicemails left without the phone ringing and droped calls in the middle of a conversaion when you both have full signal ...
I've put a compaint into O2 and if there's anyone from O2 reading this the trouble ticket is
5659018
I'd like for O2 to fix this soon as over 30 people will move to orange in the new year ...