Good shout Aqua G - SHAZZA and I were discussing this in the shrubbery only yesterday and we both believe it has gone to A (for both of us).
Our maxim, generally speaking, is if one can complete circa half the puzzle without need for Reference items then that is about right. Of late degree of difficulty has been well outside that parameter!!
If you can do half the puzzles without reference books, you are geniuses!!! But then, I always thought that you were! KM's puzzles have become much harder than those her father set - at least since I began doing them about two years ago. Frankly, if it weren't for Aquagility, Jim Jools, Sarumite, Paulineward et al, I'd give up and go to bed. Bless you all - and long may KM force us to use our noddles.