Are you planning on getting Sky TV at the address? If you are and Sky have spare capacity at the exchange (which going by the O2 problem they may not) then Sky LLU on the mid package will give you a decent amount of download and will allow the line to run at it's max speed. If you can't get Sky LLU then I would steer clear of Sky Connect.
I'm afraid it sounds like you are going to have to pay a high amount for the "unlimited" download even if you do only get a 2Mb line - it is the amount of download that costs the money not the speed at which you can get it. And as you probably know the BT charging structures aren't geered towards large amounts of downloading.
Sky cannot offer LLU at the address (although I will be taking up Sky TV at some point), otherwise I would have gone for a bundle deal on MAX or something.
So it looks like:
Sky Connect (which people are telling me to steer clear of)
O2 Access (which people are telling me to steer clear of)
Virgin National (which people are.......hmmm I'm sensing a pattern here)
Tiscali (Not a personal favourite, but by far the cheapest out of the lot)
AOL (Would not touch it with yours!)
AAISP (Not enough peak hour allowance - otherwise might have been good)
BT (Major problem in the past with them at a different address)
any more to be looking at?