The ground
West Melbury Marly Chalk · Head
The map puts Watlington on West Melbury Marly Chalk — soft, marly chalk, as the British Geological Survey describes it. Within half a kilometre to the west, Head is mapped over it — mixed clay, silt, sand and gravel washed downslope.
Expect alkaline, chalky ground, which may be heavier where the Head is present. Many chalky soils are shallow and free-draining, the RHS notes, but where there’s clay they hold more water.
Planning
Watlington · Pyrton · Shirburn · Chilterns
The town centre is in the Watlington Conservation Area, and the Pyrton and Shirburn conservation areas are within a kilometre. Inside one, tree work needs six weeks’ notice to the council (small trees — under 75 mm in diameter at 1.5 m high — are exempt), and even taking down an existing fence, wall or gate might need permission.
The centre is just outside the Chilterns National Landscape, about 350 metres from the boundary, but about 82% of the parish is inside it. Both count as designated land, so an outbuilding beside the house falls outside permitted development and needs planning permission; inside the National Landscape, outbuildings more than 20 metres from the house are also limited to 10 square metres in total.