Thank you both very much for your help.
I have now managed to get Knots up and running using the method suggested by nc50lc.
As for the Blockchain re download issue, Knots seems to have picked up the information I already had by itself without me needing to do as @nc50lc suggested.
Good, reusing the datadir used by Bitcoin Core will work.
But since you're using a different client, it would be best to let it verify the Blockchain and re-create the UTXO set instead of trusting the blocks that the other client downloaded.
Anyways, your previous node is the reference client (
Bitcoin Core) so there's not much difference in terms of block storage and it's pretty much safe to use.