From CAP 724 Airspace Charter..
The qualifying criteria and the provisions for the establishment of ATZ are contained in Rule 45 of the Rules of the Air Regulations 2007.
No they're not - I've had a look at this SI and Rule 45 is all about what the pilot will do in an ATZ
From CAA 'Establishment and Dimensions of Aerodrome Traffic Zones (ATZ)' July 2010
3.4 The CAA will consider the establishment of an ATZ at a licensed aerodrome at which an air traffic control service, flight information service or air/ground communication service is provided. Hours of ATZ activation will be limited to the notified hours of watch of the air traffic service unit or of the air/ground communication service.
3.5 The CAA will consider the establishment of an ATZ at an unlicensed aerodrome at which an air traffic control service or flight information service is provided. Hours of ATZ activation will be limited to the notified hours of watch of the air traffic service unit.
3.6 The CAA will consider the temporary establishment of an ATZ at any aerodrome in general accordance with the policy described herein, except that in the interest of expediency, the related process will not routinely involve industry-wide consultation. The operator / licensee of an aerodrome at which an ATZ is established will be required to ensure that the appropriate air traffic control service, flight information service or air/ground communication service is provided throughout the promulgated periods of ATZ activation.
So that's cleared that up then ..
