We have a large dog with full tail which he has damaged the end of (not badly). If he knocks it we end up with blood splattered everywhere, then he will be fine for a few days and then the process repeats itself. Can anybody help please?

Have you been to the vet? If not I would pay them a visit and they can give you some syringe cases which you then vet wrap to the end of the tail until it heals. This allows air to get to the tail so that it can heal up. In my experience tail injuries are really difficult to sort out as they are constantly being knocked which then opens the wound again.  We used to have a cocker spaniel with a full tail and she injured the end , after months of trying various things it just wouldn't heal and kept getting infected so had to be amputated. The only other solution I can think of is to foam pad all of the walls etc in your home, not very practical though lol.

take him to the vets and get them to put a padded dressing on it. should allow it a few days to heal.

I remember someone using an old fashioned hair roller to go over the end of the tail and thus protect it whilst healing.