I have to say I'm impressed by how well Talk Talk handled my migration from Pipex.
I placed the order online, and was told that as TalkTalk take over the BT line then I wouldnt need a MAC code.
A week or so later I got the welcome pack giving a date when the line and broadband would change over.
This morning by the time I tried to use the phone it had migrated already and after I changed my router settings everything was working on the broadband side as well.