O2 would be my choice if they unbundled my exchange.
Good luck with O2, from what I have read you should be OK.
You made the right decision staying on the 100Gig.
I know I did and as I have said before, what it the point going faster to only run out of road.
I would have to be pushed off the fixed 2Meg because as it is now I am not jumping off.
My connection is rock solid apart from it seems to shut down every night between 12 and 2am.