Out of interest, what do other air forces do re Ensign up/down routine?
In the USAF, the flag raising and lowering is performed typically by members of the Security Forces -- usually two junior enlisted or NCO, no commissioned officers present.
The uniform is usually just the uniform of the day (usually the blues -- typically shirt only in warm weather, and with a coat in colder weather). I think probably equivalent to what I've previously seen in this thread called #2 in the RAF? I've also seen it done in Battle Dress Uniform (BDU), which are the camouflaged fatigues.
The lowering and raising of the flag is accompanied by the appropriate music (reveille in the morning, retreat or taps in the evening) broadcast by loudspeaker throughout the base.
At the sound of the music, all personnel outdoors should stop and face the flagpole, or if not visible, then face the direction of the sound of the music. Military in any uniform render salute, civilians stand respectfully. All vehicle traffic should stop (assuming the music is heard).