Rog :
Very interesting post, thank you.
I believe the Clarksons Comet flights from the North-East were operated from Teesside, not Newcastle, although Dan-Air doubtless operated plenty of flights from Newcastle for others. In 1977 I was regularly visiting near Teesside, and there was often a DA 727 doing training circuits there.
I was aware of the Northeast charters out of Heathrow in the 1970s, but similarly to the BMI ones from there operating until just a couple of years ago, they appear confined to marginal time at weekends using aircraft otherwise standing idle from weekday trunk route flights; British Eagle was the last to have an actual charter fleet based there (including handling RAF charters with the seats in a Britannia turned backwards, which occasionally when things got disorganised ended up being used on Glasgow schedules in this configuration, to the surprise of the pax !).
I believe that some of the One-Eleven 500s that came from Court Line ater their collapse brought the bizarre Seatback Catering with them, and were used by Dan-Air as such.
Surprised to hear of the Wardair 727 doing a subcharter over to Corfu ! Did they sneak it in and send a westbound Canadian flight off several hours late ? I went in that aircraft in 1969 to Vancouver, stopping both ways in Greenland.