They had already declared mayday. At that point the crew get anything they desire, including a surveillance approach which was specifically asked for by the captain. Listen to the tapes. He could have asked for a PAR regardless of his instrumentation, weather, etc. and it would have been delivered, no questions asked.
Maybe the Brits think something of this (obvioulsy) but obviously, it was not at issue here. What is at issue is what triggered the faults, was there smoke, and was the crew guilty of gross negligence for landing because of a smoke warning. My guess? The crew is already back flying and the nexus of the investigation is the aircraft in question. That's the way it works here and with any luck will continue to do so.