Bit of an odd one, so I exported with a rotation of 239° or so as project rotation, and Solibri showed the drawing rotated from north. I was then told that my drawing was at the wrong angle for the federated IFC model. On downloading the Architect's IFC and looking at it in plan in Solibri it is pointing north. I had previously tried adjusting angle to 239° from true north in the georeferencing and then 'undid' it feeling a bit nervous. Weirdly the georeferencing now says 0° but (see below) my north point is pointing in an odd direction.
I then exported IFC with no rotation and apparently my drawing is now magically in the right place.