i feel for the OP. Ive got the same problem here, too the point im trying to think of ways of protecting my land. Mine is the front, when i extended the drive using gravel it got so much worse and all the cat lovers at work said its the cats that think it cat litter and so use it.
So £3k later and a nice block paved drive and its still going on, right on the paves. Like you i think all the local cats use the front garden as a meeting point.
We had the problem in the back garden and now ive chased them off (because im not watched as mush there by th emosey lot in the street) it has helped limit the problem. Out the front i cant do anything, the cats even know it i swear it.
I thought of kiling them, but like one posted has said the cats dont really understand what they are doing wrong. So i have to teach them, wihtout hurting them like shooting them with a gun. What have i come up with.....
Find the path they take into your garden, it will be the same they use every time, then go and buy 50 mouse traps. Dirt cheep to buy, now set them on the ground at the bottom of the fence. The cats wont know what they are first time round and will jump on them. They wont do it again. You cant be blamed for deliberatly setting out to hurt them as u can say you have a mouse problem. You cant be blames, the cat has now be tought and its a cheap fix.
The rat trap mentioned earlier was a thought i had too, but it meant death and not a nip.
I think cats are like their owners, selfish, ignorant and annoying. I bet if they had to put up with someone elses pets poop they would soon kill the animal.
All i got to do now is work out how to deal with my front garden problem (cant use mouse traps as its all open and theres no fences to jump down from.
ps, when i fitted a new wooden gate at the side of my house and the local pests were using it as a scratch post. i used 1 dozen nails with there heads cut of and nailed them sticking out in the area they were using. that sorted it. I wish i could have seen the cats when they scratched the post and it bit them hard.
pps, a nitro radio controlled car also works great.