Mike,
Samknows is a cracking site for seeing what broadband services are in you area (especially those that have their own equipment in your exchange - LLU), and crucially how far you are from the exchange. This is the bit that really effects the speeds. This site is also worth checking out if your planning on moving.
I have Sky TV and phone and as I live 3+ miles from the exchange i pay extra for a Virgin 50Mb package. I could never go back to 3Mb speeds now. To see a 7GB game on Steam* download in 20 minutes is still brilliant. VM do have their problems on lower tiers, but in my experience they go out of their way for top package customers. Plus they are the first to start roleout of 100Mb BB this year (September for me).Yes i pay over the odds, but I hate the VM TV menu with a passion!!
*btw if anyone is on steam my name is F9thDigi.