Performance and economy will be affected with lower RON fuel, even on the standard map. The higher the better octane wise, so venture out for some Tesco Momentum or V-Power if possible, but if not then the 97 from Sainsburys will have to do. Using cheaper fuel (95) means the car becomes reliant on the functionality of the knock sensors to continuously pull timing back to keep it safe
Having data logged both V-Power and Tesco, I've found V-Power to be better in terms of reducing knock, but there's not a lot in it. Both are miles better than anything else available.