Thank you
What's probably more important is the cost to call the network
Which mobile networks or landlines will be mostly used to call it,
and peak, or off peak / weekends?
http://www.magsys.co.uk/telecom/residx.htm
will list the call rates from residential phones, these vary:
e.g. from a BT line, O2 used to be clearly the cheapest at weekends,
now it's Three, but Three is the most expensive at other times.
Steve Terry