A corker indeed, and a fitting tribute to the Great Araucaria. Many thanks Paul, and as ever lots of thanks for all the helpful hints. I thought getting the 7s was key, combined with the direction indicators in clues like H and X: unfortunately my brain dried up tackling the 7s and when I got one (Y) it could fit the 8s in two places! Got most of it in the end (with a lot of help from you all, and a few where I am not sure of parsing) but still stuck on Q - what sort of still am I looking for? Poring through Wikipedia on Spanish Royalty has got me nowhere.
A masterwork from Paul, and I think the longest discussion on this forum I have seen.