How do I keep the cats away - my neighbour recommends trellis along all
walls and nails on the gate, has anyone tried this or do you have any
other ideas.

Try a hav-A-heart type trap and see what you catch. Animal control
will come out and set a trap here, if they are asked. You might call
your local dog pound and talk with them, they may offer you some help.

Regards,

Hal