Unless you can repell those who keep cats from your neighborhood, nothing works.

I've heard orange peel works for some people. Or to stop them digging in a particular place put some prickly branches round the affected plants.

Yes, they worked for me

but didn't work for us after a week or two. the cats just crept in quickly and then crept out after!

One of my neighbours had one. It didn't work. My cat enjoyed prowling in that garden.

Absolutely furious that they've stunk up my garden again! At least I didn't unwittingly tread it into the flats this time...
I've sprinkled a packet of my favourite lemon chilli dry rub over the area but that won't last. I know they understand it's my territory, they scarper if I rattle the keys in the door. Might need to up the jeopardy for them (evil laugh..)

The best way to stop cats coming into your garden is to have one of your own. They are very territorial animals. I never see cats in my garden because my own cat chases them away. It's her territory.

Loosestrife, my cat gave a loud "Rowrr!" to your comment, and tried to type his own answer--with predictable results! ;)
With him temporarily confined to the bedroom, and my computer rebooted, I can go on more seriously. The most effective remedy that I know of is a mulch of chunky rocks or bark where they like to "go", or crumpled chicken wire, possibly concealed by low annuals or perennials. Planting a few plants of rue in the garden can also be effective, but a few cats don't really care about that.

I suspect that prunings of something very thorny, such as berberis or pyracantha, dotted through your plants might deter them

Thorny branches, holly twigs, water pistol!

And an alsatian!

Pennyfarthing DO NOT use a water pistol on someone's pet !

Never have Hywel, too soft, me! However it wouldn't actually cause the cat any harm, probably less than a thorn in the paw, and you'd be lucky to hit the cat with a water pistol. The spray of water in the general direction of the cat scares it off!

People are very cruel to animals. Make me angry !

Andrew lol I have two male Alsatians and a cat and the cat rules 😀. Only last night I took a photo of cat on dog bed and dogs on floor 😂

My family and I use Get Off which we bought online. You spray it on affected areas though you have to redo it again after rain but hopefully by then the cats have got the message. It's certainly worked for us.

Hywel I think cats are too intelligent to actually tread on thorns- they avoid prickly plants anyway.

6X Fertiliser. My cat hated it.

Is 6X a brand name?
I've tried a pump sprayer as a water pistol, citrus peel, a catapult (to scare not hurt), physical blocks, slathering Vaseline, boot polish and WD40 all along the fence tops, ready-made deterrents, bags of pepper, chilli powder, peeing in the corners, spraying pee on the fence (not easy at my age!) yet still I'm the rest stop on the cat superhighway...
To add injury to insult my ankles were bitten to shreds this morning by fleas that must be in the grass

6x is concentrated chicken manure. It is sold as a dry powder or in sanisitised pellets. Some garden centres sell it and it's also available online

Thanks Andrew! That may not be for me then, think the Moss Side cats would sniff it out as a an invitation to eat chicken.
I bought a tube of Gorilla Glue to help me reinforce my boundaries with physical blocks. Think that's the way I need to go. Just put hurdle after hurdle across the fence top to the point that even something with a brain the size of a walnut will catch on? That with a smothering of vaseline to make it even more inhospitable, I'll set up my own little castle defences... It's my territory, f**k anything that challenges that (within reason?)

For a moment there I thought you were going to glue the cats to the fence :-)

Liking your thinking Andrew!

There's only one sure fire way, and causes no harm to any animal - you need a sprinkler wired to a movement detector - any movement in the garden starts the sprinkler running, and cats soon learn they'll get wet if they venture in. There are one or two problems though - if you forget and go out there without switching off first, and on very windy days with leaves blowing about, that triggers it too.

That seems like a fairly definitive solution?
Motion sensors can be fine-tuned within limits?

I don't know, Darren8 - I just know I had a friend who was an electrical engineer who did just what I describe,but then he knew what he was doing, I have no idea how to do it. I think there is a setup you can buy, but I can't for the life of me remember what it was called - I think I saw it on Amazon though. If i remember, I'll add it back here...

Got it, go to Amazon and have a look at Primrose Pestbye Jet Spray Repeller Action Motivated Animal Deterrent ... there's a pestbye set up that triggers a loud noise as well, but I'm told its not so effective... link below if it works

https://www.amazon.co.uk/Primrose-PestBye-Repeller-Activated-Deterrent/dp/B004YCUT4W/ref=sr_1_3?ie=UTF8&qid=1536483557&sr=8-3&keywords=motion+activated+sprinkler

Thanks Bamboo! That looks like the perfect solution. Cats always hate getting sprayed.
Annoyingly, I don't have a garden tap. I keep meaning to save some money to get a plumber in but have you seen what they charge for even basic work! YIKES!!!
I thought about getting a jack russell rescue dog but then I'm just swapping cat poop for dog poop :-)

That's a consequence of all that cheap Eastern European labour going back home - we'll shortly be back (if we're not already) to not being able to find a plumber for small jobs for love nor money... or only for completely outrageous prices. That's how it was 35 years ago before all the Poles came when I needed an outside tap, but luckily, I had a mate who was a builder, so he did it for me. Make friends with a buiilder or three!