That I didn't know...
I'm going to pay duty on the whole batch so would that be the issue sorted?
Otherwise, could I brew my own stuff in the garden?
If you didn't know that then you will need to read all of the rules and regulations about what you can and cannot do. You will also need meticulous record keeping and probably need to keep separate records of ingredient purchases for brewery and personal use. Sounds like a real pain in the neck!