Tell your fish thanks Loopy, it must be working.
Blueboy is still surviving and I actually think he can see out of that eye now, because I was right in front of the tank staring at him and he moved his bad eye to look at me. It has definitely gone down a bit, still a wee bit cloudy and a bit bulgy but definitely better. I have continued treating with melafix daily and did a water change yesterday.
Maybe it was just an injury rather than a disease, which is definitely good news, as I don't have to worry about anyone else suffering from it.