That's worth remembering if I don't want to clean the whole carpet.

White Vinegar half and half with water and put into a spray bottle, spray away on the carpet after it has been cleaned. An old Ecover general purpose cleaner is ideal as it has no nasty chemical residue that coud harm the carpet. Or a new spray bottle from a shop of course.

Anyway it nutralises the smell, house smells like a chip shop for about 20 minutes, but it is worth it as it really works, when Zoflora and other products have failed me.