Hi Gavbam,
It is a general consensus to have BT as a landline as it allows you to choose from so many other providers - one includes free evening & weekend calls to geographical numbers.
The current cheapest are set out in the thread,
Cheap Call Providers - BT landline. If you are thinking of cable as your landline provider (not recommended) then you could look at the thread,
Cheap Call Providers - Cable landline.
As for your broadband then if you're in a
Telewest area, I'd recommend there 2mb broadband totally unlimited without caps, traffic shaping. Due to how Telewest broadband works compared to broadband via a BT landline - you are more likely to get a consistent high speed from a telewest (cable) provider compared to one using ADSL delivered via a BT line. You don't need to subscribe to Telewest's landline service at all. Telewest are currently doing an offer of £14.99 a month for 12months for 2mb totally unlimited (normally £17.99 a month).
A lot of other providers, despite stating unlimited, actually may have 'traffic' shaping which basically means traffic for viewing webpages and email will be given higher priority (and therefore faster) than all other traffic which may include VoIP, P2P, gaming, etc.