Would not accept they can force this as an inter-group transfer, letter is headed 'Cancellation of Pipex phone service(s)' and refers to transfer to new provider, says Pipex phone service will cease as soon as new service is live.
I'm on full LLU exchange with TT, BT and O2 available.
Will try call to Ofcom tomorrow as I suspect others will be in the same situation.

Edited by Malwaremike (Wed 23-Jun-10 18:47:15)

They may get away with the adsl side of things ,but the voice,no,It is a change of service and technically the same as a cease and re provide ,(adsl) also it would automatically start a new contract i would imagine so you should be able to cancel without issues , if you r phone line is llu'd with pipex on their network, then the situation hits a bit of a gray area, but if your line is still bt then i would also ring bt and tell them not to allow tt to get your line