Hullo Robert- If you have the time to start this wonderful Thread at the beginning I'm sure you will find references to, and perhaps some pictures of, BEA Tridents at Luton.
They usually arrived with a lot of other stuff as weather diversions from Heathrow . The aerodrome would then become very crowded indeed. I remember diversions parking up in the gap cum car park between the Autair Hangar and the old Britannia Hangar during the period you are referring to.