Google were specifically asked to reduce the accuracy of the geocoding api whn fed a postcode on it’s own – and reduced it to district level accuracy – it’s a bit of an anomaly that yahoo actually returns unit level accuracy. This was discussed at opentech – harry metcalfe had an interesting ‘solution’ to the postcode clusterf*ck. I can’t remember the url atm. There are workarounds (like scraping google) – but they’re all a little dubious one way or another.