I've inherited a LMS 2.5 setup that is full of lots of kits that is no longer attached and just is a mess.
Is there any way I can easily delete everything and start again with a factory restored empty database?
Yes, I had thought I included that step in that post. You must delete the DFM repository file, NMSROOT/objects/smarts/local/repos/icf/DFM.rps with dmgtd shutdown. This should be the last step.