Tesco is expensive, morrisons has a lack of health food/gluten free options, Sainsbury's also expensive but not as bad as Tesco
Iceland do some fantastic deals but no gluten free/health options
Gluten free options really are quite limited, Tesco are improving but Sainsburies and Asda seem to be the best at the moment.
It's so damn expensive though

That being said, Lidl are having a big GF push this week