Hello OP
I’m sorry that you’re having a hard time at the moment.
I’ve worked in HR and, specifically absence management and reasonable adjustments for a very long time. Firstly, your employer cannot arbitrarily write to your GP to obtain your medical records. Your GP surgery would need to see written consent from you in order to release anything, and your employer should make clear to you what they would like / are hoping to achieve by obtaining information from your GP.
They would be within their rights request Further Medical Evidence (FME) with the view to understanding what barriers to work your current state of health is presenting, the likely prognosis, and whether there is anything that they can do (in terms of adjustments) to support you to return to work. The GP would then, with your consent, respond accordingly.
Or, if your employer were to involve an Occupational Health practitioner, they too could write to your GP with specific questions that they need answers on in order to write their report. Again though, none of this could be done without your written consent.
It wouldn’t be in your interest not to cooperate with your employer. That is not to say that you are obligated to share information that you are not comfortable or happy sharing, but you need to be doing all that you can to work with them to explore how a return to work (even if that isn’t presently achievable) might look.
If you haven’t already, I would attend a meeting with them to find out what they are wanting to achieve from speaking with your GP, and whether there is anything more that you can provide directly instead. As I’m sure you’re aware, and they ought to be too, GPs are stretched to their limits and so responses to such requests don’t come about quickly. OH services would allow up to 20 working days before they would even chase for a reply. So I would say it’s in both yours and your employer’s interests to try and resolve this without GP input.
If in doubt, give ACAS a call. It also could be worthwhile contacting a union if you’re not already part of one. Some would tell you that it’s too late for their input but this is rarely the case.
My last point is that, as someone upthread already said, as a very small employer they are less beholden to the expectation to make reasonable adjustments than much larger organisations would be. They would need to fulfil their legal obligations as per the Equality Act (under which you would absolutely be covered for ASD) but small companies with only one or two employees are much more constrained in terms of what adjustments they could realistically, and reasonably make, and so if your absence extends with no expected return date in sight, the potential for dismissal isn’t as fraught with legal complication as some on here would have you believe. Your employer, after all, is allowed to prioritise the profitability of the business if your absence is likely to jeopardise that. I don’t say this to frighten you, just to arm you with the facts.
I wish you well. Take good care x