Now that I've found that streamclip thingy, its so quick to recut some old videos onto iMovie. This was something from 8mm video, which I originally edited ages ago on a PC with Adobe Premiere and now I've just dropped it back into iMovie, rebalanced the colour and added some quick titles.
Five minutes and a mini tiger epic.
I was editing it at DV quality but have squished it down to 3Mb on disk so that it loads quickly. That's smaller than the original mp3 soundtrack for the whole movie.