[Londoner]

Well, in the past I've used Alpha Telecom Alpha Telecom - alpha telecom, calling card, cheap call, telecommunication, cheap international calls, cheap phone call, alpha, alphatelecom, cheap phone calls, cheap telephone calls, phone service, cheap international phone calls, cheap phone cards, and Cheapest Chat (which is a call override service - you charge your mobile up, and then the calls after that are free) Cheapest Chat - Cheapest calls worldwide. It's very very cheap - less than a penny a minute to the USA from the UK.