Seems the boys in the workshop were either on the crack pipe or there are some communication challenges on the floor...
\'Big gap\' turns out to really mean \'wont fit\' (for several reasons, as ever if you want something done properly do it yourself)
The STi callipers are clearly for ventilated rotors, apparently a feature my bugeye does not have. The bolt holes are in the right place but there is not enough clearance to fit the STi calliper between the mount plate on the back of the hub and the rotor
These are the current callipers, std Impreza items rather than WRX?
So it appears I will need ventilated rotors and hub upgrade?