Well, I didn't get charged - probably because the vet thought I was a right twit
The hole on his back has been caused by a sebaceous cyst bursting (all the gunk that was coming out of it was just sebum)
I didn't even know he had one there but its left one heck of a wound. The vet did say that it should scab over and heal very quickly. The fact he has now had 2 of them and he isn't even 3 yet means he will probably be very prone to them