On 15 September 2012, the crew of a Synergy Aviation Beech Super King Air making an ILS approach to runway 23 at Glasgow became temporarily distracted by the consequences of a mis-selection made in an unfamiliar variant of their aircraft type and a rapid descent of more than 1000 feet below the 3500 feet cleared altitude towards terrain in IMC at night followed. An EGPWS PULL UP’ Warning and ATC MSAW activation resulted before the aircraft was recovered back to 3500 feet and the remainder of the flight was uneventful.