Hey,
Thanks for that. The router is a 1600 but I've put in a 16mb stick of RAM myself to beef it up. Actually, the Flash card had IOS 11.3(5) on it as well.
I managed to get hold of the c1600-y-mz.122-40 image and used Solarwinds TFTP server to backup the old image to my PC, transfer the new...