If you have a mortgage, you will have to get the permission of the mortgage company; you will have to get the proper house building and contents insurance and public liability insurance; you will have to get permission from your local council to run a business from home and pay the relevant rates; and register with the tax office as self employed.
You many have to register with Environment Health and satisfy fire regulations - you may have to replace internal doors with fire doors and fit emergency lighting, fire extinguishers and so on.
Your kitchen will need to be inspected and you should have the basic food hygiene certificates.
There are plenty of books available - make sure you get an up to date one and understand the regulations and rules fully before you start. Your library may have a suitable book