there is one answer that i can give, and that is to visit your nearest zoo and in the gift shop they sell tiger//lion poo.
that works for my customers as i am a gardener
Save your used tea bags, dry them and sprinkle with Olbas Oil. Place these around your garden. Don't know why but cats hate it and stay away. (you'd need to keep replacing them though)
Thanks davenclaire & masma. I have problems with next door's moggies and will try these remedies. My partner tried the lion's poo one and that didn't help - maybe it wasn't strong enough ;) I've tried teabags with citronella oil before and that seemed to help .. I will give them a soak with olbas oil instead! :)