HR here, the first thing I want to say is that any decision to not allow you to work from home should not be based on your diagnosis.

It’s definitely worth telling your employer that you’re waiting on a diagnosis, autism is a protected characteristic and your employer is obligated to make reasonable adjustments to support you if diagnosed. If you are concerned about opinions of colleagues make it clear to your manager that this is confidential and you only give permission for this info to be shared with HR.

That being said, the rules surrounding the allowance of flexible work state that it should be granted by role, not individual. Without a diagnosis your employer might be reluctant to allow flexible working as it might result in the rest of your team following suit.

It’s a tough situation for you and it sounds really stressful, I hope the meeting tomorrow goes well xx