What was found
(CAN) NR 2 SPU AUXILIARY POWER CAUTION LIGHT ILLUMINATED. PILOT REPORTED CAUTION LIGHT CYCLED ON & OFF FOR 3 MINS. PILOT REPORTED THERE WAS NO DRILL IN THE EMERGENCY CHECK LIST (DEHAVILLAND QRH PSM 1-83-1B ITEM 12.8 IDENTIFIES PROCEDURE FOR THIS EVENT). LT REMAINED ON FOR REMAINDER OF FLIGHT. LT. EXTINGUISHED ON LANDING. AIRCRAFT DEPARTED GLASGOW FOR BRISTOL, IN THE CRUISE LT. ILLUMINATED AGAIN. NR 2 AUXILIARY POWER CONTROLLER REPLACED. NOW SATISFACTORY, AIRCRAFT RETURNED TO SERVICE.