There is a product called Slusher's ODORKILL that worked really really well with my incontinent beagle problem. It is expensive but it also goes a very long way.
It has been used to get rid of skunk smells, human carcass smell (sorry, that's what a testimonial said), and more. It works like the other enzymatic cleaners but this is much more powerful. I used an ounce diluted in water compared to a gallon of those that you buy from the pet stores. This was 2 years ago, I still have a lot left and I still use it to get rid of smells. BUT I don't know if they sell it in the UK, I'm in the US. It is actually sold by an engineer who "invented" it.
http://www.animal-health.co.uk/products_disease.htm
this may be the same product. Good luck!