MM wrote:
On Tue, 13 Jul 2010 11:05:21 +0100, Bob Minchin
wrote:

The hammer will be coming from the fill valve. I expect pressing the
flush gently start the refill slowly rather than quickly when doing a
'fast' flush.
Maybe changing the diaphragm in the valve will shut it up.

Looking at the top picture at
http://www.littletyke.myzen.co.uk/cistern/index.html do you mean the
white component in the right corner (closest to tiles) on which the
ball valve arm is mounted? It has a cap of some kind with "teeth"
around the circumference. Presumably this can be unscrewed?

Yes & yes. turn off the water first! note which way round the diaphragm
is fitted.

Or fit a hammer suppressor in the pipe nearby.

I could, but this hammering only started fairly recently, so something
must have happened to cause it, e.g. something or other worn after
five years' usage.

MM

Only bother to do this if the diaphragm change does not fix it.

Bob