I have had mine part,. Maybe 3 years ago. Changed a damaged rope, and lubricated.
I don't recall it being difficult, perhaps the 40 is different?
Two small Allen grub screws to back off, on lower side of drum. They don't need to be removed, just eased back to remove their pinch and location effect.
The drum and spindle can then be split, easily by hand
I may be wrong (afterr all my memory has failed me on this topic already!) I think the rope was not knotted, just "hooked over" into a Hole, like the rope on a strimmer, or the line on my fishing reel is.
The hole is in the central barrel of the drum, not on the side "flanges". Rope end then was
Sort of formed into a J hook, then the 4-5 wraps on the drum, that remain at full rope extension, will be enough to hold the rope to the drum. You could use a dab of superglue to get the rope end loaded if it slips?
This is a similar method to crane and some larger winch wires where the end of the wire is onky just tagged to the winch barrel. The wraps secure the rope, not the bitter end, which is designed to pull out in extraordinary circumstances.
I believe i do recall also the rope knot on the Barton, the Selden was nothing like that.
Sorry to hear about Selden difficulties. Bloody annoying when you've spent (what to us is) quite a bit of money!
