Possibly, the last time any serious look at enhancing the VC-10 was when BAC were offering BUA a stretched 191 seat (34'' seat pitch) Super VC-10, but by this time the merger talks with Caledonian were at an advanced stage.
Here it was mutually decided to keep with the 707-320C as the long haul aircraft initially required for BCAL.
British Eagle were apparently also offered a version of a Super VC-10 with a Combi role (I assume this was possibly different to the East African Airways Super 1153 fleet>?)
This was when the Board of Trade refused to waive the 14% Import Duty on the new 707C order that British Eagle had in place with Boeing for 1967 deliveries.
Eagle, although knowing that the Super VC-10 had much greater passenger appeal than the 707, they ultimately felt that the extra payload and range of the 707C was more suitable for their long haul charter requirements to the USA, and the Far East, and therefore worth paying the Duty with the hope they were granted the New York and Caribbean licences. (Which they sadly never got, or were reneged on)