People with more serious disabilities can use "Dial-a-Ride", since Transport for London recognize that road transport is more suited to the final 0.0001% of the public.
Delivery. Although it's a fairly new concept with US grocery stores, supermarkets in the UK have offered delivery to your door (or even a place of choosing inside your house/apartment etc!) for over a decade. I just place my order online, pick a 1-hour timeslot between 7AM and 11PM that i'd like it delivered (any day of the week) and it magically arrives.
If anything, it's even more convenient than going in person. I'm not spending ages having to drive to the supermarket, trudge round picking up everything, going through the checkout, loading up the car, driving back etc. I can place the order any time, from anywhere and it arrives when I want it to.