Encourage cat to toilet inside, not out?

KxMx

If they are not happy then they are not happy. Legally cats have a right to roam. We can't live to please others and on the flip side we can't expect others to live how we want them to.

You've been more than reasonable and gone to every effort. If they come back then be sympathetic, list the efforts you've made, encourage them to use water to deter him but ultimately you are going to let your cat out and they will have to have to deal with it, you will have to harden your heart and put your cat first.

If they keep coming back just repeat yourself until they get the message.

Fireflyaway

We used to have a cat nearby that came and messed in the garden every day. I tried repellent, bleach, pepper, fencing off the area and water bottles. Nothing worked. In the end we bought a cat alarm thingy. Battery powered and put it under the hedge and it worked. Maybe try that? 

hb2

You can buy motion operated cat deterrent sprays  -
https://www.amazon.co.uk/Pestbye%C2%AE-Battery-Operated-Activated-Repellent/dp/B004YCUT4W/ref=sr_1_7?crid=1QHW8MBG90UMP&dchild=1&keywords=motion+activated+cat+repellent+sprinkler&qid=1596724622&sprefix=motion+activated+cat%2Caps%2C256&sr=8-7 -

Maybe suggest your neighbour gets one of these - or buy one for them if you feel so inclined. They seem to start below £30.