Well, after solving the download problems (thanks edwin2win for the effort) caused by an African internet connection I then had to install the darn thing.
First attempt to "upload and install" (the first choice on Joomla's install extension page) failed - a registration problem and no patches applied (same problem as
this user judging by the screenshot).
So Plan B - use ftp to upload JMS to a temp directory on my server and run it from there using the second box on the install extension page. Worked like a charm, registered, patched and no nasty error messages so far.
It is now going to be interesting to see what I can do with Joomla/JMS on my various websites (maybe have a profitable hobby?), it is also my first time with php, the v1.0 websites were all in asp, so this is a test of Joomla/JMS user-friendliness.
If it works out then there will be testimonials, if not then goodbye €35 and a few wasted days of tinkering.