If you are just getting Broadband from telewest, then a move to the Sky MAX package would be something worth looking into if your exchange is llu enabled for Sky BB. I'm assuming you already pay for Sky TV, bundling BB onto your Sky account makes sense in terms of saving money.
You should also get good speeds from your exchange at 880 meters, although there are many more factors to takes into account for a true comparison of speed performance.
I have a cousin who moved from cable internet to SkyBB; as he had already served his minimum contract with his cable company, he could leave cable at any time, so he just placed an order to Sky BB for the Max package, and when everything was up and running on Sky BB, he contacted his cable network and cancelled his BB account with them. As the BB on cable and on ADSL come from different lines, they have nothing to do with each other so can be treated totally seperately.
F