Denham circuit height 750 ft elevation 249ft.
I learned to fly at Denham in the early 80's. We did everything on the QNH, which made the circuit altitude 1,000', very easy. The local flying area is only up to 1,000' QNH, above that you're inside the Heathrow zone, used to be Class A!
Then I went elsewhere and learned that it was easier to 'go with the flow' and use QFE 'cos that's what everyone else was doing.
Later on, I did my instructor course also at Denham and went back to QNH for everything. My first instructor job was on the other side of the airfield, where they insisted we teach QFE! (Just to spite the opposition over the other side, I suspect).
Now I teach aspiring airline pilots all-QNH but go along with old-timer PPLs in our Club who want to use QFE - just so long as we know what we're doing, that's what matters to me.
TOO