I am fortunate in having an Esso Station within five miles of home, so I can get the high octane stuff minus the ethanol. Sadly Esso stations are not as plentiful as they once were. I've had the advance and retard looked at carefully on my Beta and my Fiat 124, but need to get them carefully checked on the HF and Appia and even on my old Landy, which although made in the early 80s has a 1950s Rover saloon car engine, only lightly modernised by BL for the end of the line.
While Esso is good fuel I have had predetonation problems with my Fulvia 1600 HF (modified hi compression) and also my Gamma, both of which have correct advance curves. I do not suffer when filling with Shell Vpower.