Lodown,
Simple process really. While flying a tight circuit, keep an eye on the runway lights. If they stay lit all the way round and on final, then you're clear of obstructions...wallah! If lights start disappearing, then there's something between them and you. NVFR is NVFR.
Remind me not to come night flying with you based on this procedure!
Sequence could be something like : runway lights disappear, then WALLAH - you hit a hill you weren't aware of because you were somehow relying on contact with runway lights to provide terrain awareness.
ENR 1.5 para 4.5.2 Aerodromes without Approved Instrument Approach Procedure
IFR Day - visual approach requirements.
IFR Night - VMC from LSALT within 3NM.
Despite the mention of 3nm, I don't believe the intent of the above paragraph is for IFR aircraft to change to VFR. That would involve cancelling SARWATCH airborne, then advising ATC of the change to VFR (and ideally lodging a SARTIME) before commencing the approach.
ENR 1.5 para 1.7.2 The information provided by spot heights on IAL charts must be
treated with caution. Spot heights on IAL charts do not necessarily
indicate the highest terrain, or all obstacles in the circling area. In
addition, the charts may not cover all of the circling area. Before
commencing an instrument approach, pilots should familiarise
themselves with the location and altitude of obstacles in the circling
area by studying an appropriate topographic map.
Whilst para 1.7.2 specifically relates to the IFR Circling Approach, please for your own (and for that of your pax) sake look at a toppo. Regardless of Flight Rules, have a plan for a suitable descent point (considering obstacles on downwind and base), and forget the reliance on runway lights for terrain clearance. They won't save your life.
VI