I don’t have the cash for the camper I’d like and am not about to spend night in the back of a converted VW!
However, my folks park theirs all over the place. Their GPS’ SD card is a hub of info. They’ll often ask publicans if they can stay in a car park if they eat / drink there. They use laybys (unrestricted). They have NT membership and by being friendly with staff often get a ‘as long as you’re gone by 8’ type response to a polite enquiry.
As they’re in their golden years (is that what you mean by fair pensions and self-sufficient children?), they go away for weeks at a time with canoes on the roof and bikes on the back. Every 5-7 days they’ll go to a proper campsite to top up with water, empty the loo and what have you.
They’ve done the SW Coastal path twice without paying for a single night’s camping. They did it twice as each section was A-B-A, move, park, C-D-C…