This is going to be a very vague description I am afraid.
The show in question was a whodunnit. Each episode was a murder / mystery where a very stylised alien robot killed or committed some other crime against other highly stylised alien robots. I think it was animated, but it might just have been a motion-comic type thing. There were various clues at the start of the show, I think a couple of theories about what might have happened and then the culprit was revealed. It was on late afternoons / early evening on BBC, I think.