Thank you both for the responses.
I am considering my options still with regards to the flock. They all love their out of cage time together and when they came out today (after a couple of days just in cage to get used to their new cage mates) they all went into the old cage together for a while. Now they are settling a bit to preen and Sage has gone back to her cage and Jay is sat at the door, while the others are perches outside it, preening.
And as they all flew around the room, I noticed that my little threesome, Jimmy, Skye and Sunny, would often all follow one another and sit at the same place as the others. For example, Sunny has been trying to work out how to land on the curtain rail and she finally sussed it out today. Skye is the only other bird who ever goes on it (and he often does like to land on it and perch up there) so once she got up there he and Jimmy almost immediately were up there with her. So it seems they are enjoying their company together and are flocking together very naturally.
With regards to my females, they got on fine when they were quarantined together but they just avoided one another as much as they could. In the bigger cages they would have more space to avoid each other as well. It's always an option to do the males and females on their own if needed.
Jay does seem to like being with Sage, who seems the least social of all the birds- often returning to the cage a long time before the others do, so I don't want to move them if I don't need too.
Thanks Jo Ann for all the information. I can completely understand why it's easier to keep them apart for breeding.
Thankfully, mine flock were all aged near enough that there's no young and old birds mixing, so I don't have to worry about that at least.
Thanks for all the advice.