Ths is just the PestBye people doing poos on lots of people's gardens. The moment someone buy one of their products, they stop the pooing, and you think it was £35 well spent 🙂
If it's a patioed area, then keeping a selection of comfortable for cats patio furniture available for them to sleep on, will help. They won't poo where they are napping.
You could always release a plague of mice on your neighbours, keeping the cats far too busy to visit (pet shops or conversion to apocalyptic cult of doom depending on budget to get the mice).
I note there is advice for napalm, claymores etc. This is always a bad idea. The cats will always spot them, reverse engineer them and use them to catch their own prey. There are always innocent victims of this. Surface-to-Air missiles launched from beside cat flaps is one of the leading air travel risks.