Water feed won't shut off. Slow leak into drum. Zanussi Jetsystem 1250?

I keep having to turn off the hot and cold water feeds into my washing machine in between uses. If I forget the drum slowly fills up over a couple of hours or so.
I am reminded of this when I next open the door and flood the kitchen, an event that happens every couple of weeks and which guarantees my wife and myself a good laugh as we raid the airing cupboard for towels and splash around mopping it all up.
Mind you, our floor's never been cleaner...
Any ideas?