Brilliant! I've used Shop4Parts for years and always been very impressed. (Not tried since getting the Forum discount code...) Didn;t realise they could get parts they don't list on their website. Interestingly that tray has the identically-shaped depressions on it to that on my diesel (the 'half-cylinder ships near the front left when on the car) - so its good to know that's the part to order if ever I need another one.
One thing though: waxyol etc might be a good idea, but I still maintain the best rust preventer is the regular washing-off of winter (or seaside) salt and the hosing out of mud at any time of year. Any mud that holds water, especially salty water, against the metal will make it rust.