Mind you how about the Instructor at a large airfield who recently cancelled a lesson on a perfect VFR day because the AI was US and she did not know how to gauge steep turns...........
Might be a reason not to do the steep turn exercise (not in my book - but some might consider the demo to the stude requires it!) but given wx conditions in the UK an instructor should be capable of some flexability and gone on to another lesson - eg. PFLs, or even start the Nav.
