Cheers for the suggestions.
Big dog is currently out of the question as we have three young kids (1, 3, 5) and right now we cannot afford to feed/insure a dog. Next year though maybe.
Asking him to use the front door instead: Nice idea and one I’ve thought about but probably too close in nature to “I think you are a d***head, please leave”.
I had thought about aimlessly walking into his back garden every other week – would probably send the message.
He probably thinks he’s just being friendly.
I wish you could meet this guy. He’s like the steroid-infused lovechild of Basil Fawlty and Mitt Romney.