We have just completed an extension on our house and were told that as long as the new work did not extend further than 3mtrs from the exisiting rear wall, we could procede without planning permission. Work started a year ago this week and within a month we were up to 1st floor gutter height, when we received a letter from planning saying we needed permission after all, because we were infilling the 'L' shaped bit of our house(its a standard Edwardian shape with galley kitchen) as well as going out 3mtrs from the back and planning wanted the measurement taken from the furthest point back (6mtrs). Panic! The planning officer said "dont worry, lots of people make that mistake - but you still need permission!" Cheers! So we had a 4month shutdown. Moral here is dont rely on the internet, builder, architect or a phone call to the council, always go to the planners!