Sounds like you will need to get a re-paint to cure that. The van is now 10 years old so you cannot expect the suppling dealer to repair it for free I suppose.
Hopefully they are aluminium skirts rather than steel ones, otherwise you might be facing a more serious corrosion problem. Worth scraping a bit of paint off to find out. If it is steel gone rusty you will need a more fundamental solution than just a repaint.
I suggest you take the MH to a selection of accident repair firms in your local area to get quotes for a repaint. The quotes might vary surprisingly.
What you will prbably need is surface preparation and filling then primer and repaint. I have used a commercial caravan/motorhome repairer who does insurance and dealers' work and he quoted a very reasonable price.