It's tricky. Tony Blair is hyper-sensitive to being blamed for this. According to another question on that poll, a real Guardian liberal question, approximately 2/3 of the UK public think Tony Blair's decision to join the invasion of Iraq was largely or partly responsible for causing the bombings. So he has good reasons to be very sensitive on this issue even though this is the same sample of whom 75% thought that it was time to sling out the preachers of hate.
Tony has it right: The terrorists are responsible.....not Afghanistan, Iraq, or whatever. It's what terrorists do.
If those imams are preaching "death to the West", then I'm not sure that Britain's support of the war in Iraq would have made that much difference. I suspect that regardless of whether or not Britain supported the war in Iraq, that this type of attack would have occurred sooner or later. Maybe I'm way off here, but the isalmocrazies hate the West just because. I think Britain was in for it eventually no matter what.