"I did mix 'Relax'," Lipson says, "but because Trevor didn't know me very well he wanted to get someone else in, and so Julian Mendelsohn ended up doing the mix.
Yes agreed. I read somewhere that JM did the mix in a few hours; it's theoretically possible that he'd done another one before (or even after) the 7" but financial prudence would dictate that you get the most successful mixer in the UK in (as he was at that point) to do just the one killer* mix.
(*This is all subject to debate of course. I think at the time I actually preferred the LP mix, but there's no denying the 7" packs a punch.)