Nick wrote:

Thanks guys - I wasn't too far out in my assumptions but the replies have
served to confirm
and remove doubts that the meters are too far out in what they are
measuring...

So I will continue to fine where the consumption and quiescent drain (
some 400 watts) is going.

I'll start a new thread to see if this is reasonable.
Thanks,

Nick

You might try shutting the house down, then switching on circuits one at a
time whilst watching the meter. When you find the circuit that adds 100W,
try going around and turning all your video/dvd/tv/computers etc off. I bet
it's the combined drain of all of those things - maybe not much each
(except the PC which could account for a couple of hundred watts by
itself), but they may add up.

The blinking led on the meter will give a reasonable measurement of
instantaneous load.

HTH

Tim