Is there an employment support worker with your CMHT? I had one and she was quite helpful. If not Citizen's Advice are excellent I used them for an employment matter.

Your employer has to treat your mental illness as a disability and should offer reasonable adjus. tments that will help you do your job. That could mean offering you more flexible ways of working including reduced hours or working from home or time off for appointments. It is a two way process so your employer can' t impose changes on you and you can' t demand the impossible.

I'll PM you later with some helpful links.