Having recently discovered that the free Xserver software I was using called X-Deep (v4.6.5) was no longer free (I wanted to find a copy for my collegue), the hunt started again for an alternative.
Luckily I discovered Xming during my google travels.
This seems to work nicely with my PuTTY sessions using X11-forwarding, so my simple needs are met (and those of my collegue).
Xming is available here
The download page is here
I downloaded the file called Xming-6-9-0-21-setup.exe and it installed cleanly and quickly. It's only 2Mb.
I also needed to download and install the fonts package (xosview wouldn't run). This file, again on the download page, was
Xming-fonts-6-9-0-6-setup.exe. Again, it installed cleanly and after restarting Xming my xosview application worked fine.