Well, the converter in question isn't actually part of the c2k/legacy switch - its in a different cabinet. This set up is more simple. The fibre terminates at a patch bay in cab2 from cab 1. Two fibre cables are patched into that and the ethernet converter. The ethernet converter plugs into port 24 of my 3Com legacy switch.
The ethernet converter isn't showing a steady link light. The same thing happened to its sister ethernet converter in Cab 1 which I was able to pin down to a faulty power supply. Could well be the same as this one, but if I can get one for ?30 (which I saw on Ebay) I don't mind buying the entire thing.