hi
i have exactly the same problem but i am 1m away from the boundary and i have had a visit from the stoke on trent planning enforcement,they told me that i require planning permission but should not be a problem. but as i'm on a sloping site and the lowest point is the boundary ,if i measure from the highest side which has land against it 1m higher. they are still saying i need planning permission on the grounds that it took engineering works to level off. so it would seem that the goal posts can be moved. so you cannot use permitted development unless they say so. the other point is i have a local coucilor who lives the otherside of me whose land is 1m higher than mine at the boundary but then also slopes another 500mm so when they built a garage directly on the boundary. under their rules that they state planning would be required, in this case as they built up the land, the garage viewed from my house is nearly 5m but from the front entrance to their garage is 3.5m , they have confirmed that it was not required for the councilor hey if your face fits. the other statement i was given was that as i had already extended the house previously i had used up all my rights so permitted development was not allowed to me even if i fully complied as i have a large garden the 50% rule would ned me to built 4 houses just to be close. with all this i have asked for this in writing before i make an appeal. i know its probably no help to you,but it goes to show that you are always at there mercy.
