Excellent. Thanks all. The current flush valve has siamp stamped on it. Looking at pics I am pretty sure it's a 33a. I will get a washer and give it all a clean. 
To be fair - it's been in there over 20 years and this is the first fault. Ive changed the inlet balve once and cleaned the seat a couple of times. So I am happy to replacethe flush valve like for like especially as it should avoid me dismantling the toilet.
				
			To be fair - it's been in there over 20 years and this is the first fault. Ive changed the inlet balve once and cleaned the seat a couple of times. So I am happy to replacethe flush valve like for like especially as it should avoid me dismantling the toilet.




 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 it has a cheap krap ball valve in it there only 4 quid saw a substantial  one in toolstation for 12 quid on offer .brass mains conection  and quality plastic  float in a sleeve with a twist knob on the top  for altering  the height  flitted it in  in 5 minutes
it has a cheap krap ball valve in it there only 4 quid saw a substantial  one in toolstation for 12 quid on offer .brass mains conection  and quality plastic  float in a sleeve with a twist knob on the top  for altering  the height  flitted it in  in 5 minutes 
 
		