I went to maximum magnification on Google Earth and found that it did indeed show zero longitude as being about three quarters of the way to the far side of Black Heath Avenue, to the east of the Zero Meridian in the Royal Observatory, so then I went to the Prime Meridian site and found that "the zero meridian on the WSG84 datum, which is about 100 metres to the east of the line marked at Greenwich, is an average of the various continental movements", so we need not worry: someone is paying attention! Roger McCutcheon.