I used to work at the Grangemouth refinery, which supplies petrol and diesel for all of scotland and most of northern england ! Asda, Tesco, Shell, Sainsburys, morrissons,BP, Esso and many other petrol retailers get their supplys from this refinery. Its the same allover the country! the only difference is that when the tankers leave the gates of the refinery they put an additive into the tank which mixes in transit. This is why shell had lots of problems years ago as the additive didnt have time to mix properly at the stations close to the refinery's.
The petrol we used to make was 95 ron standard unleaded and super unleaded 97 ron. Also standard diesel / red diesel and ultimate diesel.