http://www.theregister.co.uk/2010/11/08/3uk_orange_roaming/
That could get interesting.
What I found interesting was, Three hss 2G phone users, they never sold any 2G phones.
SIM only deals?
It must be people using old handsets, so yes, it's a possibility.
Apparently they run an audit occasionally and lots of people over on 3G have reported receiving a text stating they are in breach of the T&Cs though allegedly if you just forced a 3G phone into 2G you were fine as the device reported it was 3G capable, people did this in areas where Three's coverage was rubbish but they wanted the cheap prices and/or used their beloeved old GSM handsets.