So yesterday was the day of the 1.2.1 session with +R trainer, which I eventually got to have despite being delayed by roadworks. We started off discussing how I wanted to progress, the answer being that I want to build on the advances we have made at home lately, and I explained that Cass really has more interest in searching than retrieving. The trainer said this is opposite to most dogs who become more distracted if working in cover. Her assessment of Cass is that she is a dog who wants to "work" rather than simply do what is asked of her wherever she is. She asked me to show her how we go about it at home, so I demonstrated by asking Cass to retrieve from the longer grass at the side of the field, only of course my throw went wrong and the dummy landed where it was clearly visible. Cass shot straight out picked it up, returned to me and quick as a flash shot by with the dummy in her mouth! Ha ha! Demonstrating her specialty!
So then I was taken in hand, Cass was allowed to have free roam and inspect the field before returning to me of her own volition, the rationale being that so often dogs arrive at a training venue and are expected to work straightaway, when their heads are everywhere. The trainer said that Cass didn't seem to be sure of the difference between training session and free play, so I did some work on that -- clicking and treating when she returned to me, doing the yoyo orientation with treats and building in the sit. She said that I must learn to recognize when Cass returns to me, seeking interaction and looking for "work". And then release her to "play".
Then we went into the bale alley. Cass absolutely loved this, really loved it, all that jumping and not being able to see the dummy! We did lots of that, with me learning to bring her into the heel position at sit ready to go ago again. We hadn't done it before (much tutting

) but she is used to being lured and magic hands so it's not difficult .
We discussed the use of cues, which I wanted to do as I sometimes feel I'm not very precise and muddle her, so that clarification was useful and helpful. It seems I haven't been too far wrong though.
We also discussed Cassie's eyesight, which is phenomenal, sometimes much like a sighthound.
The upshot is that I need to continue to keep the retrieves varied and interesting, in the main by ditching the plain canvas dummies and using fur/feather ones. So I bought one from her, it's got feathers on half of it, and on the way home stopped at Sporting Saint and purchased a rabbit dummy and a pheasant pelt, so I'm looking forward trying those soon.
@FayRose , I will go back for at one more 1,2.1. I'd like to join the group if I can.
Thanks if you've read my long post!