Virtually all ISPs provide broadband services using your local BT exchange (providing it is has been converted for broadband capability).
Unbundling i.e. allowing the ISPs to install their own equipment in exchanges and not have to pay BT for each customer as would be the case if BT equipment was used, did speed up overall broadband provision.
But originally BT's high costs involved in converting its exchanges meant that it started with the most profitable takeup returns per exchange - a natural business decision.
You may remember that BT used to seek potential customers' notification of desiring a broadband service from their local exchange; once a certain takeup figure was reached then the conversion was undertaken.
I watched Watchdog last night. What a banal presentation re Bulldog. The representative from Bulldog, Cable and Wireless in fact, held his hand up and accepted there are faults and they are being addressed. I thought he was honest and straight forward, he certainly took the wind out of the presenters sails, and as for the woman presenter, I suppose she was flashing her legs as a diversion. Sows ear and silk purse came to mind.
If they have to fill out their programme with such rubbish they must be on the verge of being taken off air, which wouldn't be a bad thing.