I have a deal which gives me free international calls to land-lines - good.
The downside is that it is linked to the computer, so when the internet is down, so is the telephone line. So if I need to make a call when it's playing silly buggers, I have to run to the nearest mobile reception, which is at the other end of the village!
Not much help - but if you've got good mobile reception this arrangement might be worth looking at. I'm sure this set-up would be available in the U.K.
Always assuming that distant family have land-lines, which is not necessarily the case these days, unfortunately.