This seems to be a good deal. According to quidco you also get £4 for receiving and activating a Tesco SIM pack. Tesco also do a £5 extra SIM card with £10 airtime credit.
Calls 10p per minute and Texts 5p when you top-up £15 per month*. The airtime credit can only be used with the SIM included in this pack. (*To ANY UK mobile or standard fixed line number).