I think MPS is the right place to start (and make sure you have registered with Telephone Preference Service too). We have the same problem as you Jane, and sometimes I think getting donors like my mother is just what these charities deserve. She too sends cheques for tiny amounts to multiple charities, and what with the postage, the cost of processing the cheque, the letter back to her to thank her for her donation, it must always cost them more than what she donates!! However I do grab any chance to go through her post if I can, and return letters to charities with ‘return to sender, delete from list’ scrawled across the envelope. I don’t think it really reduces the number of letters she gets but it does seem to have stopped it growing any bigger.