TMT ... it depends on your local exchange.
On mine sky and talk/talk have their own kit.
If you go to them (for both broadband and phone) you are taken off the BT equipment.
I did have a link to a site that lets you check your local exchange to see who has their own equipment installed.
If I can find it again I'll add it.
Edited to add .... found it ... use:
http://www.samknows.com/broadband/checker2.php