Exactly as stated in the beginning............"An ATZ at a civil aerodrome does not exist outside the notified hours of operation of the A/G, AFISO or ATC unit".
So for instance, Notified hours in Pooleys, 8-8, Then that's the notified hours...outside of this, there is NO ATZ. Unless NOTIFIED otherwise...eg, Notams. Then it is active during those hours! For example, Aerodrome x in say Pooleys is 08:00-20:00. NOTAMs state open until 22:00 due to night flying training. Then consider yourself notified. The same goes for open hours 08:00-20:00 but NOTAMS state closed from 12:00-14:00. Then there is NO ATZ, UNLESS, in the example above where it states in a Notam the ATZ remains active, even without ATC staff available to give any type of service.
The caveat to all of this is airmanship! Even though an airfield is closed , you may have missed the Notam extending it's hours, forgot to check etc etc but you know aerodrome x closes by 20:00 and it's 21:30 and you are about to transit through, give them a call on the appropriate frequency. Better a couple of blind transmissions than a near miss and being reported to the CAA for flight violations!
Just my 2cents....
B.