Looking at a map(not the original) I agree the spelling should be Sidley. The map in question was owned by my older brother, who obtained it when he went to school camp at Bexhill in the mid/late 50s; it showed an 'aircraft' symbol with 'Sidley Green' printed next to it (could have been an Esso Road Map and is long gone). Maybe, considering the scale of the map, it could actually have depicted Pebsham; the two sites look to be less than 2 miles apart.