Washed it! Poor thing has spent the winter flying along covered in salt spray. I expected more corrosion generally but no. I did spray it thoroughly with WD40 before winter though, a couple times. The undersides, rain channels and all those sorts of places.

I had to leave my old one in my friends field in Devon for about 3 years once before I rescued it. I saw it sometimes and always went to spray the underneath with WD40. The sill areas and other generally vulnerable bits. Did seem to keep it good.