Alonsos,
Just to re-assure you, since we have had the new gas locker door fitted we have had no further occurrence of mushrooms! I think the problem was due to the fact that we were with out one of the gas locker door locks for couple of months whilst travelling obviously letting the elements into the structure of the locker door itself. What the it was that gave the mushrooms an anchor to grow is anyone’s guess.
Don’t let our experience put you off.
Clippie