I haven't done enough research yet on UK. I will circle back to this comment once I do.
I did have a user sign up from Canada, but it's so much simpler there that it probably doesn't make sense for Canadians to pay for Mel:
1. Fill out the CMA Do Not Mail form: https://cmadnm.cawebhosting.ca/submit.asp
2. Put a note on your mailbox that you don't want to receive Canada Post Neighbourhood Mail.