The most data I've (recently) used in a month is 3.7GB, and I never use more than about 100 minutes or 150 texts in a month.
I'm currently tempted by Three's 12GB, 200 minutes, unlimited texts for £17.
The main alternative is GiffGaff, with their 6GB, 2000 minutes, 6GB data for £18.
Is there any alternative I should be aware of?
Original post on Dreamwidth - there are comments there.