Got to ask where does super market fuel come from?
Tesco/ Asda etc don’t have their own refinery’s.
All fuel is made to a golden standard so be it UKB or SU10 it has to meet the minimum rating for RON and MON etc, all fuel is blended to this standard.
Some companies such as shell have their own additive packs which they add at point of tanker loading etc.
For example in the south Esso Is the closest refinery so shell/bp/Tesco/Morrison’s etc all fill up from the same bulk plant to fill their forecourts so you can go to shell but you are actually buying Esso petrol.