I find it very hard to see why an examiner would not let the GPS be used on an IR test en-route section, after all BRNAV is a mandatory item above FL100 and if the GPS fitted to the aircraft is BRNAV approved the pilot should be tested using the kit or his IR be restricted to flight not above FL099.
All this harpping on about not using GPS is due to the CAA opps department 's head being well and truly stuck in the sand and trying to pretend that GPS had not been invented all this at the same time as the engineering guys on the floor below had been busy approving the TSO for the GPS instalations.