Oh dear, one of those puzzles that makes me feel even more of a dunce as so many are finding it easy. After grinding out the North and SE I am stuck with 21a (I have narrowed it down to a few shapes but cannot get it as am missing a crosser, 22d, 24a and 25d, none of which I even have theories about! Can someone please help put me out of my misery (compounded by year's first bout of hay fever)?