Sorry about your pain grandtanteJE65, but glad you can still ride bikes. DH struggles to do that now because of arthritis.
I’m with you in many of the savings you mention but some wouldn’t work for me.
basically living as our parents and grandparents did
3 cooking food that can be cooked quickly and thus cheaply
My parents and grandparents cooked stews, pies, and puddings, all of which took far longer to cook than many meals I make now.
5 taking very short showers, turning the water off whilst we soap ourselves
We take short showers, but if we turned the water off whilst soaping or shampooing, we’d waste a lot of water waiting for it to heat up again.
6 Re-using washing up water for cleaning bins, door-steps etc.
Using washing up water, probably greasy or containing food debris to wash anything else? I’d have to use even more water to rinse that off.
7 Always going to the charity shops first when looking for new clothes or shoes
My Grandma made most clothes from scratch and mended things as did Mum in her youth. Did charity shops exist back then? We often got clothes handed on from better off relatives, but someone has to buy the new things to pass on, or fill the charity shops.