I know where you live
hehe.
Sorry mate couldnt resist.
Dunno what you could do really mate. Think you would have to drill em really. or maybe put a dirty gret tie wrap round em. but would look w**k probably.
Best thing to do is, if someone nicks yours, nick someone elses. Its a vicious circle! You never know, you might end up nickin your own back! Or u could take em off it dodgy areas or at night.