You can try a product called 'Skunk Shot' - it's a repellant that keeps pesky animals away (and it STINKS!) - although I haven't tried it before, I used to sell it, I do know it works though.
http://www.skunkshot.com

Otherwise, anytime you see the cat, you could spray it with a jet of water from a water pistol or spray can (the spray n wipe kind of stuff).. I don't know if I'm making sense because I don't know what products you have in Scotland that are like it. Cats hate water, and this technique has stopped my boy Siamese from making mischief after we go to bed (ie, racing up and down the hallway for 1/2 an hour).
Good luck!