I am fairly sure that I recall seeing a Dan Air Viscount at Gloucester some 35 years ago. My memory tells me that Dan Air flew to Isle of Man, Jersey and maybe also Carlisle. My recollection is that HS 748's were the norm---but I'm almost sure that on at least one occasion I saw them fly a Viscount into Staverton.
One Poster has also mentioned the Dan Air Comets. I recall splendid return Clarksons Holidays flights from Gatwick to Valencia in September 1966 or 67. Was the aircraft perhaps G-APDK ? What I do know for sure is that it "made" my holiday to be going and returning by Comet 4 !