There are national groups run by charities or experienced home educators that have a wealth of information on how to get started, what to expect from the Local Authority etc. and are a good place to discover the ins and outs.
https://educationalfreedom.org.uk/
https://www.educationotherwise.org/
https://www.home-education.org.uk/
There are also national Facebook groups that are worth connecting with for advice, support and to keep up with anything that might affect home educators from a national/legal perspective, here are some popular ones:
Home Education For All (HEFA) UK
We highly recommend that you also join the local groups on Facebook:
These are public groups that you can join to find out more, even if you’re not yet home educating. Once you are a bonafide home educator(!) both public groups have a private, sister group that you can join – see the featured/pinned posts in each to find out how.