We have it good in Australia, VFR over the top is great in places like Melbourne where it might be impossible to get over the mountain ranges without this rule. Otherwise you might be stuck for days. Not sure 100% on heli's, however for fixed wing, you need to have a positive position fix every 20 minutes or the pilot and aircraft must be night rated as a minimum with VOR or similar plus pitot heat etc. When I say the pilot must be night rated, that's how to ensure that the pilot is signed off for a VOR or similar.