Friends of us have just sent us this... it is a sim card which you can get for free but calls to UK are 0.5c p min (landline) and 19c a minute (mobiles) and 15c texts - no connection fees etc. I think it looks pretty good from here but being a techo phobe I have no real idea. Perhaps someone on this glorious site will have a looksee??
Lebara Mobile - low cost international phone calls from your mobile