Thanks all for your support 
The guidance on trans issues certainly implies that children who do not identify as girls are expected to leave; it's also clearly stated in the new membership criteria that only people who identify as girls and women are eligible for membership.
I have written to Girlguiding to ask for clarification on this. Is the starting point that gender non conforming girls are welcome to stay on in their units for as long as they want, or until the natural end of that section?
Or is the starting point that we expect to them leave and leaders should help GNC girls navigate this?
These are two very different positions.
As ever, Girlguiding has not responded. More silence.
If Girlguiding will not engage with its leaders, or answer reasonable questions from its own members who have to apply the policy, then we have no choice but to make this public.
I'm now aware that people who write to Girlguiding more than once about this will get a template email noting that no further responses will be given if you contact them again, and concluding with a little dig about how GG accept that not everyone is as inclusive as them.