Mark,
I can only speak for myself, working for a charter airline. We do get breaks on night flights, however these are only for an hour or so and are taken in the galleys. On charter aircraft, unlike scheduled, there are no crew rest areas with bunk beds etc. We try to catch a few zzzz's sitting on a bar box or our crew seats. Breaks are always and should be made in rotation.
Scheduled airlines maybe somwhat different. I agree it is appalling if no one could be found in the galley. As a purser myself, tha would be just bad crew management. I believe on certain aircraft ie Boeing 747/777 there are specific areas for the crew with bunks and rest areas. Can anyone confirm?
On night flights I would always get the main service completed swiflty so as to allow the customers to rest. but would clearly state that we are always available should we be needed. I insist the crew make regular patrols through the cabin with water etc, approx every 20 mins. There is nothing worse than being trapped in a window seat gasping for a drink and not being able to move!
Granted, many airlines do things different ways. Some good, others not so.