Many thanks Alexander - that's brilliant! 🙂
And thanks for the tip about the categories.exe - I hadn't realised that existed so I'm sure that will prove useful in the future.
The window doesn't dock at the side, like the ArcCatalog and Search ones, as I had hoped, just disappears totally but at least I now have a hold of the window so I can play with options which is a massive step in the right direction!!