I remember an comment from Jan Chappell that she was never that happy with the way Cally was written but as a fairly new actress at the time didn't think she really had power to speak out to the writers and producers.
Don't recall ever seeing/hearing anything from Josette Simon on her experiences. On Youtube there a 3 behind the scenes/retrospectives with the cast and crew for the first 3 season (never got the funding for to cover season 4) and I don't think she featured.
Of course it could just be crappy memory.
The character problems for Dayna were probably made worse by the introduction of Soolin.
And we'll pretend that animals was never made.
From my 'Behind the Scenes' book.
Sally Knyvette, who played Jenna in the first two series, had also decided to leave the series at the end of her two year contract. She had found the role frustrating to play, and was increasingly dissatisfied with the scripts she was given. "I would liked to have seen Jenna realize more of her potential. She started off as this really exciting, intergalactic space pirate, but then she became sort of the housewife on the Liberator - not quite that, but she did become very much a Blake sidekick, with one-liners and supporting remarks to the lads and making sure she looked as sexy as possible. I did lot of teleporting; I usually had to fight for things like that, but the character wasn't anything like the way she had been conceived in the beginning. I think the relationship with Cally could have been more interesting too. She was an intelligent telepath from another planet, from whom Jenna could have learnt. I was a representative from Earth and all these powers as an intergalactic space-pirate; as a team, I reckon we could have got to Servalan in a week or two. The fact is, we not given our voices; it's a sad and simple as that. There was no humour either; that's something I really got fed up with, that there was one drama after the next, and always trying to survive it. My mother used to go berserk. She said, 'When are you going to smile?' In twenty-six episodes, I smiled maybe twice. It was all very much on the one-dimensional level"
Jan Chappell had been unhappy with her role for some time and decided to move on. "I just lost heart in the middle of the third series," she explains. "It had been on for three years of my life; I only had one other job in the meantime, because I had seven months of Blake's 7, and five months off with my son Sam, who was quite young then, and I just got restless. I was bored, and you're bored with the character you're playing, you're not going to enjoy being around other people, so you're going to be a potentially destructive influence."
"I was asked if I'd do four episodes in the fourth series, and I said no. There was a professional reason for that because there is a danger that you can get away with three series, but never four. In fact, I didn't do another tv job after Blake for eighteen months, because I forgot that they repeated the show. That was another reason for not wanting to be a part of the fourth series. I wanted out, completely."
Both Josette Simon and Glynis Barber declined to be interviewed for the book.