We only use VOIP, voipblast.com is the cheapest we have found.
Although it charges 3.9 euro cents connection, one can go phone to phone for no additional charge. That's from Spain, no reason to think UK would be any more.
Of course calls to most 'western world ' countries are free, just the 3.9 cents, and calls from Pinas to UK etc are free too, but of course one needs a computer to make the link.
