TALKTALK_SUPPORT:we wouldnt be able to sign you up unless you got BT to activate your line.
Just to clarify abit further, as Talktalk have a habit of not making things clear. From my experience working for the Post Office and the amount of calls where I got through asking to "Activate my line" for talktalk, even some cases the talktalk agents would just put their customers straight through us at the Post Office pretending we're part of their company. BT, and no other company, will activate your line for talktalk, it would make no sense for one company to start up a line for another company and the activation of a line can't be done by itself, a package has to be chosen for the line to be activated on, otherwise you'd get a free telephone service :)
Talktalk are, at this moment in time, unable to start up BT lines so if you really wanted to go with Talktalk then you would have to go through a provider, such as Post Office or the Ultily Warehouse who have no minimum contract for their service. Then once the line is up and running you could transfer over to talktalk