Foghorn plumbing

[Squishey]

The diaphragm in my downstairs toilet had split so I replaced the whole syphon. While I was at it, I also replaced the fill valve and ballcock. After this whenever we flush either toilet or run a tap that's connected to the CW tank (including hot taps) we get the pipes reverberating causing a noise like a foghorn.

I've had a Google and that suggested that I may have used the wrong restricter in the fill valve. I swapped that but the noise continues.

Any other suggestions?

[Squishey]

I've replaced the fill valve for one with an integrated float but I'm still getting the occasional groan. I don't have a local service valve so can't turn the toilet pressure down.

Is it likely to be the ballcock in the CW tank 'bouncing'? Air in the system?

Any pointers would be much appreciated.