[Frank Stacey]

The history is that when I noticed an overflow from the cistern and went
to fix it I discovered the flush pipe connection was leaking at the
cistern end. It's taken a while but, with some useful tips from here,
the flush pipe is now water tight again.

So to the float valve - no chance of repairing the original so needs
replacing. The brass replacement I have has no "silencing mechanism".
The water issues into the cistern from a 12mm diameter hole in the brass
body. Any suggestion please for how to fit some sort of tubing to
silence the flow?

I see that modern variants of the float valve have no long arm and
float but the float rides up a vertical guide. None of the on-line
sources I can find give the dimensions of any of these attractive
alternatives. I don't think there is any possibility that they are small
enough to fit in the cistern "round" the siphon base. So I might swap
over the float valve and the overflow inputs to the cistern where there
should be no problem with space for the float valve. Is it worth the effort?

Apologies for the length
Frank