Re 16dn, I put it in the wrong way up at first, and realised my mistake when I solved 14a and 19a. I wasn't irritated because the clue does work both ways so I saw it as a bit of clever misdirection, but perhaps I'm being too kind. Certainly if 14 and 19 had been harder I would have been complaining. But my overall complaint is as above: too easy, and perimeter too random.