OK, I've sussed out a way of dragging and dropping images into pre-positioned boxes in one move, so that is OK
But, they still align to the top left-hand corner of teh frame, rather the the centre. This is despite the frame having align to centre set up with their object style.
Yeah, that looks like a bug.
Well, it's good to know it's not just me.
Off to find out how to report an issue now...