Hi Pete, the car must be damp inside to be that mouldy. You should first find out if and where the water is penetrating. Could be blocked drain holes (very often below the windscreen) or entering through the boot or windows. It shouldn't be that mouldy just because it has been standing outside and not used. I use Bactoshield from Dry Fusion as I am a Dry Fusion user. Clean it off and put the air con on ( that will suck the moisture out of the car) Once dry and in use you shouldn't have a problem.