Quick question for the electrical boffins:

AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or
rubbish?

My question is how is it measured? I've stuck my AVO across the incomers to
the main fuse box, and can get the voltage down to about 216v if I switch on
about 6.5KWs of electrical load on the property - without any substantial
load the voltage is nearer 250V. So, under what load condition is the
voltage measured?

Thanks Julian.