So, gasax, you consider that the rules are for other people and not for you?
"Unexpected" PPR? Perhaps a little more prior planning and preparation might be of assistance in preventing pi55-poor performance.
GPS doesn't transmit, so will not be a problem to the aircraft equipment.
"somewhat immune"? What is "somewhat immune"? Sorry, but either equipment is certified immune or it is not. I don't think you're ever likely to see a placard stating "THE EQUIPMENT IN THIS AIRCRAFT IS SOMEWHAT FM-IMMUNE"
In some aircraft, I grant you, it will be less of a problem than others. However, unless the CAA grant exceptions based on every airframe in the country (and every pilot's level of ability and experience) then they are naturally going to go for the safe course.
Maoraigh appears to have nothing in his aircraft but a single Nav unit - no VOR/ILS receiver, no ADF, no transponder and no pilot to get distracted from his #1 priority - flying the aircraft.