I finally found some software which appears to do exactly what I have been looking for. It's called ImageNest. You can drag and drop multiple images and it 'best fits' to your media size for you or 'nests' the images :-)
So what's the problem? It's only available on Mac! Whilst I do (reluctantly and probably not for much longer) have a Mac, I want to be able to use the software on my vastly superior PC :-)
Anyone seen anything similar that runs on Windows?