The aerial images available as backgrounds (Bing Maps Aerial, Esri World Imagery and Mapbox Satellite) are fairly clear especially if supplemented by local knowledge.
The legal boundaries shown on the OSMUK Cadastral Parcels overlays look a bit more complicated than might be expected but might help. There is a slight alignment difference between the images and the Cadestral Parcels but the shapes should be of use in providing some information to help with mapping.
Any improvement to the map helps, does not need to be perfect.