What have people used to seal the fuel filler neck to the body.

I am using Mk 2 Escort filler and reused the old cork seal but want to replace that for a new one or similar now fitting it all back together.

I can get a sheet on the bay quite cheaply, but only 1.5mm thick (Im sure the old type is thicker), but also get Mk1 seal but that comes with the filler.

You can make your own from almost any material as long as it is petrol resistant.