Handing in my notice

I haven't been in this situation. So I can only suggest speaking with people who are specifically trained in this area, employment lawyers, citizens advice. Macmillan website may also point you in the right direction. 

Hi, I agree with McQ14 - do check with the MacMillan employment advisors. You are have certain rights and protection under the Equality Act. Without knowing what your job Is/ was, your employer has to do certain things such as consider applicable reasonable adjustments (like working hours or location such as working from home ) or even changing your role temporarily, to take account of side effects, appointments, fatigue etc

I used to work as a care assistant in a home so this is why I decided to finish myself 

For benefits they may now class you as making yourself intentionally unemployed.  Speak with MacMillan for advice or if you in union them.  If public sector do not ever resign, let them finish you then you can fight for your ill health pension.