Ian, l have two numbers the main one my business line at home, the other one in a neighbouring towns approximately 8 miles away.
Had it put in my sister-in-law's house as an extra phone, cost to install at the time £14, I pay normal domestic line rental plus calls, plus diversion to my office phone.
This works very well and doesn't cost as much as the BT option as you mentioned earlier, so if you have good friends or relations in other towns, it might be worth asking them if they wouldn't mind you putting an extra phone line on , and may be cleaning their carpets for nothing now and again to pay for it (this is what I do) all the best Ted