OK

I was googling cat proffing a garden and this site came up

CATS - Cat Advice - Cat Information - Cat Pictures - Cat Forums

It has a lot of useful info including a receipe to get rid of cat urine odour/stains using bicarb and lots more - including how to train your cat to use a human toilet!

Teach your Cat to use the toilet - No more litter trays

I have actually heard of cats who do this before I came across this site