I have DH-122 as a competitor of the VC-10 and DH-123 as a twin engine high wing passenger aircraft, not unlike the Fokker F-27, that was abandoned in favour of the Avro 748.
I know Hesham says 're-allocated' in both instances but where does this information come from. How reliable is that reference source?
As far as the Jet Craft MJ-II (note the Roman numerals) is concerned, I found the following in Flight International 29 May 1969, page 892, reporting on the 1969 Paris Air Show: "Jet Craft Ltd Las Vegas (US 25, S) The stand displays models of the 17-seater twin GE CJ-610-6 MJ-III Mystery Jet commuter and corporate aircraft and Six-Seater R-R Viper 522-powered MJ-II jet—de Havilland Vampire T.55 derivatives. Jet Craft's MJ-T1 two-seater trainer (a Goblinpowered modification of the Vampire T.11 by Marshall of Cambridge (Engineering) is shown in the aircraft park and will be demonstrated." The page also has a picture of the mock-up of the MJ-III but I cannot duplicate that. Maybe somebody got better software.