Re: I want to know the equipment...
I did similar a couple of years ago in the UK. Im with Zen Internet and have my own router, so cant plug a analogue phone into their own box.
So purchased a Grandstream VOIP set, plugged into a RJ port on router, signed up with Sipgate Basic (for free at the time), chose a landline number. Then... filled in some paperwork to Port my landline from BT to Sipgate. A few days later, I have 2 landline numbers that can ring on my VOIP phone - I didnt need the number I chose, so got them to remove it. Then installed a little app on my mobile that can take calls from SIPGATE and boom, I get my landline calls coming to my Granstream phone and mobile. I never make outgoing calls, so it continues to cost me nothing. No line rental, nothing.
Unfortunately Sipgate dont do this deal anymore, and I guess its only a matter of time before they write to me. But certainly any VOIP provider who can port your landline from BT to them is going to be cheaper than BT by more than half or more.
Im still shocked at how they can charge so much when they are on VOIP... oh wait... its BT.