I doubt he goes to a Sainsbury's in Chipping Norton but I'd imagine he'd go to Broxham or perhaps even as far as Banbury. Can't imagine a quick trip to Oxford unless he makes a day trip of it. And lets remember this is the guy who, if he does live a lot in Chipping Norton, he's not going to be entirely stationary. He'd be going back and fourth from there to London as well as many other events. It's not wrong to think it's implausible that he'd have the time to just go to a random Sainsbury's miles away when he's the Prime Minister who has to lead a government and country. Fair doos to the man for actually being able to remember the price of milk, even I have no idea how much milk is.