Is there a Bullmastiff Rescue anywhere? I have a friend who is knows of one and trying to help find a home for one after a marriage break up and said husband is threatening to PTS?
They have been trying hard but no-one seems to want to help?
Try either Iron Mountain Large Breed Rescue or Large Breed Dog Rescue. Both are easier to contact through their Facebook pages as there is usually someone on-line every hour or so. Both are fantastic and thoroughly assess and vet/homecheck/support adopters but I think they may have a waiting list. Worth a try.