Welshwife we to have carriers we bought from France in about 1998 from the Champion store. We use these in our caravan for taking our washing stuff over to the showers. Like you we fold them up properly, very good quality.
I must ask you all, what do you put your rubbish into. I use supermarket carriers for this purpose to line my under sink bin. Therefore, if I don't use them, I have to purchase bin liners. Is this saving the planet? What this does is give more cash to the supermarket instead and I am worse off, but bags are still being used.
As someone mentioned here, Sainsbury charge 40p for any number of carriers that are used for home deliveries. Our daughter shops this way, so she gives me all these surplus bags which in the main keep me going.