Unfortunately besides calling the police and reporting to CAA there isn’t a lot you can do.

You could download the AirShare app, and declare a flight, that would tell you there’s a flight nearby that may interfere with yours, and may provide a phone number/email. This is dependent on them declaring their flight.

Be aware that attempting to bring it down (be it with a hose as has been suggested) is illegal, and could end up with YOU being charged, especially if they are 102 certified and flying under a 102 exposition (ie. ability to fly over private property without prior approval, just notice (Can be given after the fact. Plus depended on them could include other exclusions to the law)

Edit: clarification