the author posted this shortly after your comment:
" I've taken it down for a little while while I upload the most recent version that has a lot of small errors corrected. It will be back up in a couple of hours I expect. It's worth the wait..."
So it doesn't seem it's a bandwidth issue so much as a quality issue.
The download is huge because I made the figures in Inkscape and it can't produce compressed PDFs. If anyone knows how to solve this problem, I'd be happy to hear about it. Mail me at s.prince@cs.ucl.ac.uk.