I'm not sure if it's the way it's worded Martin but it looks like UKman wants UK calling cards. We have the BT Int option at £5 a month for unlimited calls. Post office one seemsed fairly reasonable.
We use calling cards ourselves when in Florida so there are no surprises when we get home and advise our guests to do the same as there have been cases where Guests have used "unlimited" calling plans and found either they or the homeowner has been penalised under the "fair usage" clause they all put in.