Hi All.
Thanks for the prompt and interesting replies. The reason I asked the question is because I recently visited the Met office in Darwin and was surprised to see they measure air pressure on the first floor of an airconditioned building rather than measure the actual atmosphere outside at ground level. They actually report QFE as the pressure at the level of the barometer and not at runway threshold level. This means, in Darwin at least, that QFE is out by about 0.5hPa. Probably not much to worry about if using whole numbers (but I'm not sure about that)? They reckon that the pressure readings are near enough so they're good enough. I don't know if they measure the pressure the same way at other offices; I would hope they take more care with other met readings though! Might be a good idea to remember this one when using pressure readings in Darwin? I wonder how accurate their QNH readings are? I'd hate to think dodgy pressure readings have had any thing to do with CFIT accidents; hope not.