Thanks guys for the advice.
I took the screw out already, seems to be holding pressure so far.
Dezzy, I will try the soapy solution method to see if the remaining hole still leaks slowly, thanks.
That's what I was worried about, if there is no hole all the way through, the repair shop will still make a hole and patch it anyway.
Maybe if its not leaking I could fill the hole from the outside with vulcanising solution or this stuff?
http://www.mikes-diving.co.uk/storms...glue-297-p.asp