Optimax at full flow in my local Shell. They have rebranded normal undleaded as 'low suplhur' and made the nozzle a light blue colour.
personally, I just go for the cheapest muck at Tesco and Sainsburys. Recent Buncefield highlighted the fact all standard unleaded comes from the same place. I say this as I have a mad relative who swears that her car runs roughly on TEsco supermarket unleaded as it 'isn't as good' - insane woman.... I shop at Waitrose don't you know......