Re: Amp used by Jeff Beck on "Cause We Ended as Lovers?"
Not emphatically sure, but some clues here...
According the "The History of Marshall" (Doyle), Mr. Beck used the plexi 50 watter (1987 model) for a long time.
IIRC, he also used a Colorsound Overdriver for a time.
(BTW, highly recommend "The History of Marshall" for all the Marshall-heads out there. They even include schematics!)