I have a 1973 VW Beetle U.S. version.
One day I bought all the necessary hoses to connect my charcoal filter. Eventually the big hose that connects to the air cleaner sagged and got partially chewed by the fan shroud cooling fan. I eventually disconnected the charcoal filter by cutting off the big hose in the engine compartment. I just got tired of having to disconnect it every time I removed the air cleaner. What helped the most in eliminating the smell of petrol or fuel in the cabin was trimming the ends of the small hose(s) and any other hoses that connect to the top of the gas/petrol tank. One of these small hoses had fallen off. Replacing the rubber fuel sender gasket or seal was a big help too. Another thing that helps is not filling the tank all the way to the top until it runs out.