It's not impossible that British efforts along those lines are even worse because we know that they did play with (not quite as "move fast and break things" as the CIA) LSD, but there's no real pressure or habit of properly declassifying material from the depths like this (MI5 do publish a little, SIS do not at all, ever... no matter how hard you ask). What little MKULTRA material exists was preserved almost purely by luck, IIRC.

I also don't even want to imagine what the Soviets got up too - they'd probably laugh at Enhanced Interrogation.