So after rolling our a machine which was installed via WDS I went to change the product key on the Office 2010 installation, as per usual I navigated to Programs and Features in Control Panel, found office, clicked Change and chose the Change Product Key option, went through the wizard, rebooted and to my horror Office said it couldn't activate and closed after clicking OK.
It's the first time in years I'd come across this problem and lots of articles said to do this, that and the next thing, even on the Microsoft community forums there were a million ways to fix this and none of them worked.
One of the answers was to use this app which asks which version of Office you have installed, but upon running it it said it could find no information about the Office install - I guess this is why Office was failing to activate.
A bit more digging and I found another site with some reg files you run ... Whoa, hold your horses! Before running any program or registry mods found on the internet, I suggest first researching the app , running it in a VM to make sure its safe and scanning it with Virus Total and opening the reg files in notepad to check they're not going to do anything nasty. Always. No exceptions.
I found this blog which describes his own troubles which were different, but we needed the same end goal - to remove all traces of Office having been installed. I removed Office 2010 through Programs and Features then ran the reg files, rebooted, reinstalled Office 2010 with the correct product key - et voila it now activated and worked like a Office product should. Please do head over to his site and have a read of his post too.
Having read the comments I noticed Microsoft had put out out a Fixit to remove Office when you were unable to remove office normally, but decided as I was able to remove Office I would proceed with the reg files instead.
Here's the Fixit in case you are unable to remove office in the usual manner: https://support.microsoft.com/en-us/kb/971179
and a mirror of Office Scrubber files "just in case".