It was more to check its definitely the pipe you think. Noise and vibration can travel, its possible if you live in flats that its someone else...
Any pictures of the boiler? Could the pressure relief have been capped off or isolated?
Try shutting the valve while it's creaking
Any rodent problems?
If you can, get someone to turn the water back on while you wait in the bathroom just in case
Best to get the installer/builder back to take a look
Any radiators getting hot?
Are the zone valves accessible in an airing cupboard maybe?
Sounds like it might not be wired correctly and calling...
Can you post a picture?
Are any pipes under the boiler hot?
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