It's strange how it happens so often : 2 minutes after my last post, I solved 3 of the queries I had raised. No such luck with the last 2.
19Ac What of Roman Britain's capital? (4) ?U?D Looks like QUID or QUOD, but I don't see why. 26Dn Clown losing hat : which you like? (3) A?Y Looks like (Z)ANY, but why?