Also MucOff do some anti-rust spray. Won’t be as good as a full clean up, treatment and repaint but as a simple preventative measure it might be worth it in future. It’s in an aerosol so easy to squirt it around. Used some on exposed bolts under the van and it’s lasted almost a year so far keeping them in nice rust free condition.
I got it for bits on the bike that seem to flash rust after cleaning and was impressed so thought why not try some on the van