You say that you are originally from Essex but now you live in Cambridge .
England a British Subject
Depends... some would say "from all over" - listing all 3. Some would say England, or the UK.
You might also identify with one, more than the others.
The answer can also depend on the purpose of the question. Some who ask it really mean "where do you live?"
You are from wherever you call home.
I have just returned 'home' after 20 years away. I wasn't born in the town I am in, but spent my childhood and have most memories from here.
Depends on who is asking, a teacher asks where you were born... you are originally "from" where you were born, a friend asks you to meet them and asks where you are "from" which is where you live now
You are from the United Kingdom.
Wherever you were born