hi got piper carvan ?

Clear all seating cusions out give them a going over.
Look for water stains which could indicate a leak.

Mix a bleach and water mix not too strong and give the whole of the inside a good clean even inside the cupboard under the seats. If it has a fridge give that a clean inside with a desert spoon [level] of bicarbonate and about 3pints warm water.
Go to nearest caravan spares shop for toilet tanks cleaners, and a cleaning agent for the cusions. Don't use a wet one as they are buggers to get dry if the foam get too wet. Once finished washing in side put a fan heater in c/van to assist drying out. All smell then should have gone.

Bob
May 2009