Thank you so much for your replies.
It is a large company and, like most large companies, the headline is that they are very hot indeed on anything that falls under the 'inclusion and diversity' umbrella, but people's anecdotal experience is often that, at a lower level, they don't always live up to their ideals - e.g. denying flexible working requests (not that that is something which would personally help me).
Is this the type of change with a project or comms team who could offer a timeline or are looking for 'champions' to support the change?
I've no doubt there will be local champions but they tend to be selected rather than volunteers. It would be an idea to engage directly with a champion, though, as they tend to be more approachable than managers, so I will look out for them being published. If by any chance they do ask for volunteers it certainly wouldn't hurt to wave my hand!
How do you think yours would react?
It's hard to say - from my point of view I feel I get on OK with my manager, but I was moved into a new team at the start of 2020 so I don't feel I know her perhaps as well as I would if I'd worked with her for two 'normal' years. I'm just a bit shy of 'announcing' it I suppose because it would make me a focus of her attention which I hate - I'm the sort of person who just prefers to get quietly on with the job with minimal intervention.
Whilst you're waiting for an assessment, you can self refer to Access to Work (ATW) to have an assessment about your work related requirements,
I had no idea a service like that would be available pre-diagnosis - thank you very much for that information, I will look into it.
I was able to bury myself in a complicated piece of work this afternoon and I feel a bit calmer now it's been put on a lower shelf in my brain for a while, but it's sort of simmering there and I'm very nervous that I'm going to spiral again and start blurting, or even firing off emails which I'll later regret.
Like many large companies, mine has always been the sort of place that can't go for more than a year without having a restructure of some kind or completely changing working practices, and now they have decided the pandemic is over, there really is an 'all change' atmosphere, and I function very badly in that environment - I need routine and stability (I know I am far from alone in that)!
Thank you for all your suggestions, they really are helpful.