I've personally never had an issue with any fuel in any garage, nor have I ever noticed any performance or mpg differences and I'm not fussed at all as to what brand I'd use - I use whatever happens to be nearest when the fuel light comes on. I would obviously be wary of using an unknown / no-brand garage, but so long as it's a big filling station with all the branding... then... I fill away.
Beyond that is overthinking it IMO, but I know this is a strangely divisive subject, so each to their own.