Maybe I should have phrased it slightly different.
GPS can only be used as a primary means of navigation if the equipment and installation is approved and certified and correctly indicated in the POH/AFM in accordance with EASA AMC 20-5. Otherwise it may be unsuitable for RNAV/GNSS operations.
I am not going to teach a student anything to the contrary.
In the UK, there is no comeback on an instructor.
So my FTO is paying a fortune for instructor liability insurance for......??