Hello,
I use a Linksys Pap2 unlocked VOIP box from ebay. This connects to my Dect BT phone.
I have virgin media cable broadband, so I don't need a BT phone line and have recently cancelled with BT
It's just over 1p per minute for landlines any time and just over 9p per minute for mobiles.
The money I would have paid BT is now going straight on calls.
I have a geographic telephone number. It has Caller ID. There was a good configuration guide online and it's has been working ever since.
The website is great to use and I've found out you can change your number. I chose a really catchy one from Ballycastle, Co, Antrim, but the gf wanted a Swindon based one.
If you have cable BB without a telephone line, I highly recommend it.