Accounting help – clinic at home

Hi After 15 years part time domicillary, I have set up a clinic in a room attached to my garage. Can anyone with a clinic at home tell me how they account for this please? I have never used an accountant as I know enough to be able to do simple accounts and my tax return myself, and would prefer to continue to do this if possible as I have lost most of my domicillary customers (I had to…