I'm not in the UK, however I did some quick googling and had a read of a few things about autism workplace accommodations and where you might find support to advocate for that. Is your work something that would be possible that you could do from home? If it is I think it's reasonable to discuss an arrangement where you work from home on certain days. Otherwise have a look at these links. The first link has good suggestions of how to approach your work again about reasonable supports and links to that second link which is a grant you can apply for to support that process. The last 3 talk about various accommodations and the last one in particular is about autism fatigue and burnout at work. Hope you can get the support you deserve.

https://www.bristolautismsupport.org/reasonable-adjustments-at-work-for-autistic-adults/

https://www.gov.uk/access-to-work

https://www.autism.org.uk/advice-and-guidance/professional-practice/employment-adjustments-tips

https://www.autism.org.uk/advice-and-guidance/professional-practice/anxiety-workplace

https://www.autism.org.uk/advice-and-guidance/topics/mental-health/autistic-fatigue/autistic-adults