What price rises?
The bottom-end VM broadband has been £18 per month for a long long time......
Sky Broadband is very cheap (from £free to £10 per month). But, it requires both a) a BT landline & b) a Sky TV subscription.
There's bound to be other deals out there for ADSL broadband, however they'd all obviously require a BT phoneline. Plus, anything really cheap would probably have a catch, such as a tiny tiny usage limit, or a slow speed, or whatever.
Have a look around
http://www.thinkbroadband.com/ etc etc.
Virgin do a "2 for £20" bundle for Broadband "M" (2mbps) plus phoneline rental.