broadband connection with ntl phone line?

Hi

looking at getting broadband put in, i've currently got a NTL telephone
line, am i right in thinking that the only option open to me is ntl's
broadband options? , most other places seem to need a bt phone line

i'm only after the 150k service or around which ntl do for £18 a month with
free modem, connection and first month, i could change to a BT line but
would it really be worth it? , found most places are around £17 - 18ish a
month for that kind of speed service

ta

Chris