The BUA Viscounts by 1968 were down to the three ex-Hunting-Clan (one of the BUA constituents) series 800 aircraft. These had started out operating Hunting's "Colonial Coach" services in the 1950s, to East and West Africa, via multiple intermediate points, and indeed nightstops, along the way, which took several days each way. These services eventually became BUA's nonstop VC-10 routes to these destinations. It was therefore quite a come-down for the Viscounts to end up on UK secondary domestic routes ! The Viscounts were sold the next year to Arkia, the Israeli domestic operator, for whom they were the mainstream fleet for many more years until finally scrapped.
The Southampton to Glasgow route was begun by Jersey Airlines (I now read) on June 2, 1962, with Heralds. Just one week before this, Jersey had been taken over by BUA; in fact it was a complex arrangement because the actual takeover was by Air Holdings Ltd, who were the intermediate holding company between BUA and the various shipping companies who were the principal BUA shareholders. Jersey carried on under their own name and AOC until some years later when they were rolled into BUIA.
The strike referred to above was considered to be principally due to the personality of Alan Bristow, the new BUA chief, who had taken over following Freddie Laker's departure from the role to set up his own airline (he had fallen out with the shipping company owners over investment plans for jets for holiday IT flights). Fred had been the MD of one of the original BUA constituents, and headed up the new company for some years, including placing the first ever order for the BAC One-Eleven (a task he repeated some time later for his own airline). It was felt that if Fred had still been MD the upset and the strike would never have happened. Bristow had come of course with another Air Holdings constituent, Bristow Helicopters (still very much around today).