Isolation give the virus nowhere to go, but people need to go shopping and precautions are 100% necessary.
During the entire expedition to the supermarket, do not touch your face, hair or anything. Best to wear disposable gloves and take them off when you get back into your car. Be aware of what is inside your ‘bubble’ and what is outside.
When you return, unpack the groceries yourself onto a bench, do not let anyone else touch your shopping bags and put them back into the car for next time. Food for freezing or goes straight into the freezer and it is probably safe to assume that food for the fridge will also not breed any stray viruses but I would imagine that minimal handling by supermarkets of packaging would be a given.
Then wash your hands, take off all your clothes and have a hot shower.
I think a major vector for infection has been missed. I think it is quite likely that a virus could survive on fabric in droplets of sweat or possibly inherent moisture. Yes, your hands are the main path to your face, but your clothes also could incubate. So all of them into a laundry basket.
Then do not use the car for at least a week.
Be safe and protect our health services!