AIP ENR 12.8.4 Tracking Requirements. Tracking requirements for a visual approach include the following:
a. A pilot in command must maintain track/heading on the route progressively authorised by ATC until:
(1) by day, within 5NM of the aerodrome; or by
(2) night,
- for an IFR flight, within the prescribed circling area; or
- for a VFR flight, within 3NM of the aerodrome; and the aerodrome is in sight.
b. From this position the circuit must be joined as directed by ATC for an approach to the nominated runway.
So the 5NM doesn't apply at night... unless your "type" circling area kicks in at 5NM... However the when ready track for final is complying with part a. "As authorised"... If they just said "Cleared Visual Approach RWY 33" you would only be able to alter your authorised tracking inside the circling area.