There are small LED lights that are solar powered which you can deploy around your garden. If they come through a small gap in your hedge etc then just point the spot light and sensor directly at the gap. When they stick their head under to check for danger it will trigger the light and the cat will quickly stop using that gap. Worst it will do is muck up their night vision for a bit.

Similar to this.
https://www.thesolarcentre.co.uk/products/Thea_Solar_Garden_Spotlight-341-83.html


Everyone loves a Morgan. Even me, unless it's broken again.