It didn't seem rude...I did presume the three males had moved in one round of moves so to speak and I wasn't aware M'buti was moved beforehand. I suspect it was because Bristol haven't really got the room for more than the breeding pair really.
I don't know if there is any point moving M'buti from Chester- I think he will breed successfully when he is mature, and he's just as likely to with the Chester female as anywhere else(like Marwell) I feel.
I believe M'buti is/was interested in trying to mate Stuma but isn't regarded as being old enough to cover her properly yet. He was certainly very interested in her when I saw them in adjacent enclosures a couple of years back now. How old is he now- about six or seven?
Possibly the arrival of the Marwell male disturbed her somehow and disrupted her cycle. That male did not stay very long either so I don't think they gave them a decent chance of success. I still think M'buti will succeed with her in time.