our semi detached has a boundary fence between us and our neighbour down a sloping garden. on our side we have shrubs approx 3m high which take up a lot of space. We want to remove them and replace with a wall inside the existing boundary fence which will remain. The wall would be 2.45m above the highest ground by the house and approx 6-7m long. My understanding is that as long as the wall is not attached to our property and is on ourside of the boundary it is pd? Does this mean as long as it is freestanding i could build wall as long as it ha a gap, can this be very small, 50mm? so we can have maximum deck?