I have used mothballs these seem to act as a deterent,another tip is to use a portion of a garden hose,these give the appearance of a snake,cats shy clear,also try plastic water bottles,fill with water,seal and stand uprigt in the borders,these give a reflection as the cat approaches,they immediately sacarper as they think it is another cat,failing all else try the coleus Canina plant,cats hate them,last resort get a dog arty hughes

Try mothballs! Keeps badgers off areas I don't want them to root up!

Or buy a 'Cat-watch' electronic cat scarer- ok in small open garden. Works for a few years, except for deaf cats!!

I also have had trouble with cats, I found crushing moth balls and scattering where  they go helps, at least for some time.

I had a cat or a fox not sure which digging in the same place in my garden. Whatever it was did not cover their toilets and I had the horrible job of clearing this each day.  I tried putting garlic cloves on the spot and so far they have not come back to use this area as a toilet. Just breaking a garlic bulb and scatter either in a particular area or ramdomly. I did not crush the garlic or bury it. It seems to have worked because they have not come back.  When I put in my new plants this season I am going to invest in garlic gloves and scatter.  Hopefully I will not get invaded by Garlic plants.

i find puting plants in close together stopped cats and keeping lawn cut mown short i also tried a metal black cat scarer attached to a stick so that it swings with the wind which they dont like