I was always taught 500' QFE however I really think that it varies airfield to airfield. There was (still is ?) an southerly runway at Fowlmere which demanded a late final (150-200ft) because of a bird reserve (Pooleys not to hand, is it still there ?) . The one I always find a bit unsettling is Luton 08 if you get asked to orbit left base. Going around and around at 500ft above Luton town centre is alarming in case something goes wrong. I generally orbit somewhat higher and praise the fact that Luton has a good long runway and that ATC there are as good a bunch of guys as infest control towers anywhere in the universe (grovel)