In NZ the restriction is not below 500ft, over built up area's it is 1000ft. Even if your are in the countryside you have to put a virtual cylinder around ALL structures 500ft wide and 500ft high... get your measuring tape out..... you are only allowed to proceed below this height with an instructor on board for the express purpose of practising FLWOP- remembering said rule about structures STILL apply.
Otherwise you have to head to the Low Flying Zones we have here,... and again only with an instructor. A mate of mine is being prosecuted by the CAA for this very thing.
Glide Approaches or simulated forced landings are TOTALLY fine on airfields, its good to practise, if I'm on my own i always do one... as long as of course ATC say ok, if you are uncontrolled make sure there is nobody else in the circuit, you may not be popular.
Chop the power halfway along the downwind leg and have a go.