The top three are the only ones in it, IMO. It's either going to be Starmer, Long-Bailey or Nandy. Cooper won't pick up enough 2nd and 3rd choice votes, because she's too far to the right economically and too associated with the Blairites, as well as being instrumental in stopping brexit. And the rest of them are joke candidates. Not serious contenders.
Long-Bailey won't pick up many 2nd or 3rd choice votes. She either needs to win on 1st choice votes, or she won't win at all.
I think Starmer is the most likely winner, because he'll pick up the 2nd choice votes of almost everybody apart from Long-Bailey supporters.