"It's not the same at all, Bowlersarm. It's being able to get up on Sunday morning, spontaneously decide to jump on the bus down to Columbia Road for the flower market,"
You don't need to live in London for that. There are plenty of trains.
"No advance planning, car, or expense needed other than an Oyster card, because lots of what I mentioned is free or cheap. "
Most people have a car. We got up on Sunday morning and drove into London, no advance planning or expense other than petrol (free parking). Other times we have done the same on the train. It's not expensive.
"Mind you, we chose a tiny flat in zone 2 precisely because it was close to two tube stations and on several bus/night us routes from the west end."
How often do you use the night buses? There are night trains, too, depending on where you live (e.g., St Albans, Three Bridges, Luton,e tc.)