Spoke to soon. An almost £3 price jump? I've only been with them for 6 months. Might well take offer to leave (assuming anyone can point out a better alternative).
Edit: Orange have offer at £10 if your an existing customer... I'm not (o2) but think my dad has PAYG? Might be worth the switch if only a matter of principle (and the £70 quidco is good as well).