I spent an hour or so this weekend working out my exact latitude and longitude so that I could see the Google Maps photo of my house. Now it seems I may have wasted my time as there is a margin of error in Google’s co-ordinate system.
Lloyd pointed me at the Register story. Here’s a map showing the error. If I remember correctly, the meridian follows the thick grey line down the centre of the brown roof in the middle of the main observatory building.