I've just been to Shell, I only got 1/4 tank as they want £1.14 a litre and 95 is only £1.05, it's not 9% more potent so it's cheaper to drive the 15 miles to Tesco and get a tank of their 99RON for £1.07
Talking to the payout chap, while complaining it's not worth 9p a litre more, he said it's 99RON and that's what the flyer says.