HOW MUCH?

X, most fuel companies supply the petrol stations as well as their own stations…

You dont see tesco and sainsbury's oil refineries do you  :dontknow:

Plus my local Morrisons have just dropped under ?1 again    

the high octane stuff is the same as normally unleaded too. it's just got an additional additive in it to reduce any losses in hydrocarbons due to evaporation.
all fuel comes out of the refinery at 100-120 ron.

oh and v-power etc have an additive in to reduce carbon deposits which is nice.