You need to look very carefully at
a) What you are currently paying for within that bill. I'm guessing that's line rental, broadband, calls, the whole lot.
b) What the *other* providers are offering - most of those offers will be for Broadband ONLY, and you'll still have to pay line rental and calls on top (in most cases, some do provide bundles, TT is one of these).
It's a very competitive market, and you can often save money by just calling up your existing supplier and moaning about the cost...
A good place to compare offers is
www.moneysavingexpert.com (not a comparison site!), and read up the articles there. Bear in mind though, that Mr. Lewis' prime focus is on price above all else, you may want to then read up on the quality of the cheapest products before making your decision.