I have filled the grid but am unable to visualise "splitting" it to accommodate what I am pretty sure are the correct 5 words and would be most grateful for any pointers in that regard.
I’ve been staring at the completed grid for a day alongside the source material but inspiration eludes me. Can I check that I have the right bit of the source?
According to the source, [circled cells] (7) means (1, 6, 3, 4)
You've clearly got the gist of what's required but a 7 letter word comes first (a letter count should then give you a good idea of how to proceed for a symmetrical finish).
I'm surprised you've had to wait so long for a hint (people getting on with their Christmas preparations is my guess).