If you want to keep your mobile phone and do not want to be tied in any lengthy contract, then why not grab T-Mobile's Solo SIM card offer.
At £20, the Solo 20 comes with a 30-day contract duration and allows you to keep your phone and number. It also gives youu 600 minutes and unlimitetd texts to use any time, any network.
Alternatively, the £30 Solo 30 increases your minutes allocation to a whopping 1400, certainly one of the best offers under the UK sun.
But if you are thrifty and a moderate user, then Solo 15, at £15 per month, will provide you w ith 350 mintues and 650 texts.
Inclusive minutes and texts are from the UK to all UK mobiles and numbers starting with 01, 02 or 03 at any time. This doesn't cover Jersey, Guernsey and the Isle of Man.
Grab T-Mobile's Pay Monthly Solo offers here.