for leaks, if you can see the water meter readout, turn off all taps, washing machine, dishwasher etc, make sure the toilet is not running from being flushed, and go out and see if the meter is still showing water being used (numbers increasing). if so, then maybe a leak, or maybe a bad meter? if no one else is home, perhaps you can check again in an hour.

I am going to replace the existing copper water pipe that runs from the incoming mains to the boiler. This is due to an extension and change of the incoming mains. Currently the incoming is 25mm MDPE which at the moment reverts to 15mm for a distance of about 8m which then goes to 22mm for about 6m then reverts again to 15mm for about 2m before.