As above , when my cistern is nearly full the 15mm copper pipe starts oscillating , sound like note on trumpet , my neighbour's not impressed it resonates through his house, I can damp it down with a towel.

What happens to the cut off valve to cause this?

what type of valve and cystern do you have, plastic cystern? plastic bottom fill ball valve, side entry brass? there are several causes depending on the setup, and not all that obvious.

you may need more pipe suports, though you can buy quiet castern valves now that are almost silent

start angle grinding bits for the car inside the house. he will soon change his mind about the noise.

Check that the mounting through the cystern is tight, if it is a plastic cystern you may need to fit a metal reinforcing plate which is usually supplied with a new ball valve, any movement either from a loose fitting or wobbly plastic cystern can cause the resonating.

It could also be wear in the ball valve itself, easily remedied with a new one, only about £5.

Just replaced a noisey cistern filler that sounded like a fog horn for the last 15 secs of each fill. It was the old bottom entry ball valve and front mounted lever type filler. Now replaced with a kit from Screwfix with a whipser flow filler and pushbutton conversion for the lever. Less than £20, 1 hrs work, near silent and much faster fill - Job Done as they say!

Then no. 1 son went and dropped a china soap dish and cracked the bloomin' pan

In a trumpet the sound is created by air flowing through a small orifice. The cistern will be doing a similar thing when the valve is closing. You could try changing the washer (although I'd just replace the valve and be done with it, they don't last for ever).

Is there a kit to convert side entry front lever to push button?

Thanks Dave O

This is the kit I fitted - the button fits ina standard sized lever hole top, front or side and is on a flexible pipe back to the flusher unit.

http://www.screwfix.com/p/fluidmaster-button-cable-dual-flush-bo ttom-inlet/58353

Trip to local hardware shop, packet of 2 washers £1 ,sorted!!!!!!!!1

The only thing I can see is that the old washer had a bit of a circular dent where it sealed, may have caused some strange flow when closing making the pipes resonate.