Get an Orange Sim and put it on the Canary tariff,buy a £10 top up and get 100 inclusive
off-peak minutes,and your £10 to use as required.
http://shop.orange.co.uk/mobile-phones/plans/paygPlanList.jsp?selectedTariffName=CanaryThen buy the inclusive 100 anytime minutes bundle for £5 and get a further 100 anytime minutes at the follow on rate of 5p per minute using the remaining £5 credit.
http://www1.orange.co.uk/service_plans/payasyougo/extra_minutes.htmlYou can also build up £12 phone fund credit over a year , enough to get a free basic replacement handset .
http://www1.orange.co.uk/service_plans/payasyougo/phone_fund.html