@Mark
Yes they have to charge BT Retail the same wholesale price, that will fix all the monopoly worries won't it.....
Lets stop and think about this, we Have BT Group which owns BT Wholesale and BT Retail.
Now they could charge a wholesale price of £200 per MBit making it uneconomically viable for everybody. However does BT retail care? BT Retails buys at £200 per mbit and sells it to customers for £1 per mbit making a loss of £199 per mbit for every line they sell. BT retails end of year look pretty horrific as they make a big loss, but BT Wholesale make a killing of £200 per mbit.
BT group take the loss from BT Retail and absorbs it with the profit from BT Wholesale making an overall profit of £1 per mbit. Excellent, all competition crushed, everybody on BT lines and they have followed OFCOM's instructions to the latter. Give it a couple of years and everybody will be using BT and the competition will be dead and they can lower the wholesale price to something reasonable, or just whack up the cost for end users who are now stuck with BT....
What if competition starts up when they lower wholesale costs? No problem, we just whack wholesale up to silly prices for another year and watch the competition go out of business and then drop wholesale prices back down again, rinse and repeat ad infinitum.
Still not worried about the monopoly that is BT?