[defaultrouteuk]

@Raion is gonna hate this because NFS mounts that don't exist will cause you headaches....

Anyway FWIW I found that the easiest method for me (YMMV) was to use a NAS as a man in the middle (Synology, OpenNAS, FreeNAS etc will work).

1) Use a simple switch to attach you WINDOWS box, SGI and NAS. (probably your home router will have a bunch of ports)
2) Create a volume on your NAS and share it using NFS and Windows (CIFS/Samba etc)
3) Mount the volume on the SGI / Map the volume on Windows
4) Sit back and enjoy how easy that was. Drag and drop files and see the miracle of networking.

SFTP however was the most accessible method as most have pointed out. It works (out of the box) and I'd recommend FileZilla on Windows (or Cyberduck on a Mac).

Best wishes to all
Richie