When I was a kid, Shell garages were everywhere, now I don't have one within 20 miles of home. I have only ever used Tesco or V-Power (when I can find it) and I can't tell the difference.
95 RON doesn't actually damage the engine does it? I was told by my dealer that they are only allowed to put 95 into any of their forecourt cars, so their demonstrators run 1000s of miles on the low octane.