Why is my flat suffering water hammer?

WIAWSNB

Lorian said:

I agree and ultimately the pressure wave being created is bouncing back off something.

The OP could possibly get a suppressor soldered in where their supply enters their property but it's likely easier and cheaper to do it at the source of the rapid valve shutting. 

Making sure pipes are properly secured in clips can help a little but won't fix it in my experience.

Like I said though turning the stopcocks off just a tiny amount can sometimes be enough.

Yeah - the miscreant neighbours'... :-)

Mr R, would it be easy to fit a shock-arrestor just after your SC at ground level? That would hopefully capture any shock from the other supplies, before it travels up to your flat. 

(Are you sure that every flat has its own individual supply...?)

twopenny

There used to be a horrible annoying noise from en suite loo being flushed in both mine and the linked bungalow, both have the same pipe work.

When I had a new bathroom fitted elsewhere and something changed and mine stopped making the noise.
Tracked it down to the stopcock being opened a tad more.

I told my neighbour and she adjusted hers.

Result, peace 🙂

I had fiddled with the stopcock after advice on here but I was probably too gentle with it. Just didn't hit the spot.
Always worth a try but perhaps your neighbour needs to do it as well.