I rented the Image disk from Netflix many yrs ago, long before the HMV release was available.
If I remember correctly, the "Toby Dammit" portion included the English soundtrack, but remained problematic because the subtitles were forced and actually translated the French (or Italian?) soundtrack (as opposed to the English dub.) Obviously, the dialogue differed significantly in many instances, and the presentation suffered.
I assume that the English soundtrack was also an option on the Vadim and Malle segments, but I can't remember. Maybe the Fondas did not dub their own English dialogue. Obviously, the real attraction was "Toby Dammit" with Stamp's own voice.
And I think that the English soundtrack on that Image disk was taped off a TV broadcast. It was obviously inferior to the quality of the French soundtrack.