In general I would not be too sure about which brand is good, which brand is bad on any given day. You are very likely to find that the petrol in a given area will all, or nearly all, have come from one refinery and will all be from the same production train and will all be the same on the day it was produced and will all meet the relevant specifications for octane etc. On another day it will be different due to the different fractions available to formulate the fuel on that day, but will still meet the same specifications and everywhere will get that batch of different fuel regardless of the branding on the pump.
If you want to get fuel that is always made up of the same components in the same proportions then you will need to get yourself some reference fuel or much more economically, some race fuel at barely more than £4 a litre plus delivery, storage and so on for the cheap stuff.
The reality of ethanol in pump fuels is that if you have seals, sealants, hoses and diaphragms that are going to deteriorate in the presence of ethanol then they are going to deteriorate...it might(?!) be a royal pain to update these components but it might not actually be avoidable except in the very short term.
Ethanol is here, there's going to be more of it and even if it turns out to be the politically convenient blind alley that it may well be it is going to be years before it can possibly go away. Of course, should that happen the politicos will find something to replace it that will rot ethanol compatible materials.
If this sounds unduly pessimistic then apologies, I don't like the situation either and can think of much better places for high ethanol levels than petrol; Talisker and Bruichladdich are two that spring to mind.
