i agree it`s very confusing, I ve just searched and can`t find a broadband only offer, although I do know they do one.
The thing is though, I know my daughter pays a few pounds a month more for broadband, than I pay for broadband + phone line and free weekend calls.
She does this because her daughter would run up large phone bills, so although it`s more expensive, she saves money in the long run.
I would give them a ring to find out the options, then if possible order on line as this usually saves money.