So that you can compare, Shell Energy are currently charging their existing customers the following monthly prices for their broadband contracts (which include line rental but with no call charges included, except as stated below):
11 Mbps download speed: £21.99
35 Mbps: £30.99 (after an initial 18 month period at £27.99*)
63 Mbps: £35.99 (after an initial 18 month period at £29.99*)
[* = new customers also get three months of calling credit]
As I currently pay £22.82 per month for broadband only, with my line rental on top of that, (at the same sort of speeds as Shell provide for £21.99, including line rental) that doesn't look too bad to me. (I'll be sticking with my existing broadband company though, as it's a firm that mainly supplies large businesses, rather than home users, and therefore has to provide excellent customer support).