Hi Barry and Penny,
Our A54 had the same problem as did another A54 we know of. Both were replaced in Martinique by the Amel service point in Le Marin. They use a hydraulic jack to lift the mast slightly after loosening the stays. Once they have lifted it a few centimeters they remove the remains of the old compression disc and insert a new one (made from a different material).
I'm not sure if this will help you given your location, but I'm sure the do the same exercise in La Rochelle, France. Maybe they can provide you with additional guidance on how to proceed and supply you with a new disc.