Can I suggest? I

I always have but as I do not like advertising my full name and address because not everybody shreds it I put my house number and postcode in case anything needs to be returned.

My daughter and family have been receiving a card every year addressed to some previous occupants of their house, for whom they have no forwarding address. It's gone on for 15 years now - they have come to feel these people are long-term friends and they put the card up with the rest. There is never an address on the card or the envelope. Presumably the intended recipient continues sending to these mystery friends, but never includes an address or stops to wonder why they don't get a card back in return. Or perhaps they've died, who knows?
There's a lot to be said for the Continental habit of always writing the sender's address on the back of the envelope.

Very reasonable suggestion, actually. I will do that from now on.

Having received a Christmas card every year for last 8 years from a lovely friend who’s address and telephone number I had lost, I was delighted to received a card again from her this year , but this time ,hurrah ,her new address and telephone number was included. We had a long catch up,
I will now always include my contact details on cards as even with today’s modern technology it is still easy to lose people!

You can have your post redirected when you move, they charge a fee for that.

All you need to put on the back of the envelope is the word "from" and your house number and post code. No more detail needed so it takes no time to write.

No, you are not unreasonable. I have never understood why return addresses are considered not quite right in Britian, everywhere else seems to use them.

The British postal services might like to consider doing the same as ours, letters are re-addressed to your new home for six months, after that they are returned to sender, addressee unknown, or if there isn't a sender's name they go into the dead letter office.

And yes, adding your full name and address is a good idea, too. Yu can have small stickers printed with name and address after all.