Cat,
As a first time buyer you have now discovered the virtual monopoly that the dinosaur BT still manages to cling onto. After years of being ripped off by BT and watching them make outrageous profits, I finally got rid of them, replacing them with Bulldog. Off course they still own the exchanges, and they charge any 'independent' telco's a rent, so they still get paid.
There is light at the end of the tunnel, since it's only a matter of time before a wireless service is made available which will make hardwire connections to houses obsolete, and hopefully will bring about the end to this ex-state monopoly.