Under the new uk drone laws three categories define where drones can be flown.
These categories are:
Open: Operations that present a low (or no) risk to third parties.
Specific: Operations that present a greater risk than that of the Open category, or where one or more elements of the operation fall outside the boundaries of the Open Category. Holding an Operational Authorisation - similar to the former PfCO - allows you to fly in this category.
Certified: Operations that present an equivalent risk to that of manned aviation. This category is for high-complexity missions.
The Open Category is broken down into three subcategories:
A1: Fly over people.
A2: Fly close to people.
A3: Fly far from people.
Each of these subcategories has more specified criteria of where/how your drone can be operated.