all fuel sold in the uk has to meet a minimum ISO standard
all fuels sold in the UK do meet those standards
some fuels sold in the UK have addiitional addatives , supposedly to give more MPG or stop carbon etc
there are no available test results (indipendent) for the average man in the street to compare with lesser known brands like supermarkets

the major brands pay £ millions in advertising , this will not be taken from profit , its simply added on to the selling costs

as we know , modern fuels go off quickly , fresh new fuel comes from a well used garage \
last word : my local morrisons often has cues forming around the block , but irtonicly the well run bp garage a mile up the road is only 1p per litre dearer , thats about 35p a fill up , its not worth the stress of the morrisons , where you are stood in a line whilst people pay for there weekly shopping