Especially good if your new pride and joy had a previous owner who obviously "overdid" the perfume (I think she must have been putting it on in the car).
Pull the belt out all the way,stop it retracting with a clothes peg or bulldog clip, then soak it for a while in a container of washing powder solution. Scrub with a nail brush if neccesary,rinse well and leave overnight to dry, keeping it away from leather trim etc.
Just been Googling to find out how to get vomit out of seat belts and our Audi's manual says specifically don't use chemicals, except for a soap solution.