sunseeker
Many thanks for the supportive replies! Another letter has arrived this morning - bank's name is printed on the envelope.
I certainly don't intend leaving the house today and I won't be passing a post box until sometime Monday, which means the letter won't be collected until Tuesday - hope it isn't anything important!
I can't bring myself to mark "gone away" on the envelope so will continue to re-address post for the time being, although any similar texts from them and I may change my mind!
You really are being too accommodating of people who are abusing your kindness and consideration!
Can you not text them and ask them, politely but firmly, to inform their bank(s) of their new address and, at the same time, tell them that any further mail addressed to them will be 'returned to sender'?
I think that is, legally, all you are obliged to do.
What if you decide you don't want to go out on Monday? But you will, won't you, because you're going to feel compelled to send the letter to them!
You are being too solicitous and obliging and they are taking advantage of your good nature!