If it's the one I'm thinking of you mean the Dolphin system, used your house as a landline until you were out of range then used the Dolphin aerials dotted around the area.
They went bust some time back.
If it would work for you you could always use the wireless phone from Vonage, it uses any open (or secure if you know the key) wireless internet connection to make and receive calls. Costs about £6 p/m and you can have any area code you want.www.vonage.co.uk
I use them for VOIP and have found them to be very reliable.