You need 4 things for Cat III ops:
The airfield to be Cat III - LBA 32 is OK.
The crew to be qualified - All Jet2 crews are LVO trained.
The aircraft to be Cat III -5 Not sure this morning.
The weather to be 50ft cloudbase and 200m RVR.
Only an assumption, but if other aircraft were able to get in then 1,2 and 4 were probably satisfied. Could be that the aircraft had been downgraded.
Rudolf