OK, time for an update here, I managed to get the beady one in the harness for a few minutes. The getting on wasn't really the hard bit, it was the realisation that she had something on and under her wings that really got to her and getting it off was wayyyyyy more traumatic!
She gnawed away at my fingers pulling bits of skin up and eventually the little nips did bleed which is the first time she's really drawn blood from me.
She was half stressed (her little body heated up) and also half wanting to play because she was making the little excited noises she does when she plays. I think she was really confused as to whether or not it was supposed to be play time.
I'd quickly mixed up some of the bottlebrush loritreat which she was delighted to enjoy once the harness was off.
I did a quick test to see if she was still ok with the harness when it was off by gently running it against her and she didn't flinch or seem too stressed over it.
None of the others have had any progress with the harness, our youngest Millow who we thought would take to it the best is horrified when it is around. Blue we knew we would have problems with so she may never be harnessable. Red we knew would be very slow progress, but he is going better than we thought. I didn't expect M-Star at all to be as accepting as she has been and it's a credit to our relationship as to how she went yesterday.