Well I tried to join BT but the offer I saw is apparantly a fault on the system and not available then the bugger on the phone hung up on me!
That wasn't very good. Oh dear.
What I would do is ring them back, tell them your a Sky BB customer and you were just ringing to enquire if they could offer you any deals to tempt you away, as you've been quite happy with Sky, but you are willing to move if the price is right.
And you never know, they may offer you a discount to get your business. And if they offer you a free £5 a mth YouView box as well, rip they're right arm off.