I got a 5m VGA cable and plugged it into the projector. Now people can connect their laptops to it. I don't know what the resolution is, but 800x600 seemed to work OK.
Does the Forest want this cable? I got it for tomorrow night as I couldn't think of another solution. If so, I'll leave it and get some money. If not, I'll take it away again.
Also, someone had done lots of unplugging of the composite cables along the window wall. I joined up as much as I could, but there is still a lose end near the sound desk, and there is also a composite plug not plugged into anything near the ceiling by the projector. These things might ruin someones plan to show a DVD.