Hey Walter
I don't know about the Nexus plan, but do remember it being around, but an OK general arrangement of the ship (dating from the 1935 rebuild) and an excellent midship section (original builders) are available from the National Maritime Museum.
It is from these, and a slightly more complete set of original builders plans of the near sister ship Westward Ho available from the University of Glasgow Archives that I am currently drawing up what I hope will be an very accurate set of plans for this class of ship.
Hops this helps a little, if I can assisrt further, don't hesitate to ask.
Regards, Andrew