A company's terms and conditions, even if you signed up to them, cannot break the law. You are being fobbed off. Some companies will try to tell you anything, imagine if a company had it in their clause they reserve the right to push you off a cliff and then when you're in intensive care them telling you you've signed a contract.

http://www.ofcom.org.uk/telecoms/ioi...num_port_info/ is the legal info you need. SubCore is right about it being an EU wide regulation, the only thing is porting applies across networks not within networks which is why you have to transfer the number off a network on one contract in order to transfer it back onto the network on another contract.

I have not seen any MPD or T-Mobile terms and conditions that prevent you doing this.

Edit - In fact I remember when ordering my handset from MPD they ask you during sign-up if you have a PAC, which throws out the window what you say - are you sure you are not confusing it with something else?