If Oust doesn't work, just head to your nearest branch of Pets at Home and purchase this:
http://www.petsathome...simple-solution-15448
It's guaranteed to kill any 'biological' odours. Don't let the price put you off; you'll find that the bottle will come in handy for all sorts of things, such as when a child throws up over your carpet or when you spill milk onto your car seats.
However if you want to save a couple of quid you could buy this bottle (which is a scented version of the same product, in a smaller bottle):
http://www.petsathome...simple-solution-15468
Chris