I came across this plan from TPO mobile today after comparing it with a few others like ID, Talk Talk, Three, Life.
TPO are offering 50% off their first month on their £10 plan 30-day SIMO plan.
1 month SIM Only contract - 300 minutes, unlimited texts, 2GB of data for £5 in the first month and then it goes up to £10 a month.https://www.thepeoplesoperator.com/sim/paym/landing
Here is the page straight to the deal: http://thepeoplesoperator.com/sim/paym/orderdetails/86
Looking at their site all the plans also give 10% of a customer phone bill to charity.