Hi just a quick note if you check out the site GB GRID FREQUENCY it shows an accurate reading of current frequency on a meter and as a graph the readings tie up exactly with my own meter and seem to be much more reliable than dynamic demand ( sorry)
I USED to find the dynamic demand site useful, but agree that it has become much less reliable recently. The frequency display on dynamic demand used to update every second or so, and therefore displayed short term fluctuations. But it is not working at all at present and the more slowly updating but more reliable National grid site is to be preferred.