The postbox TW11 204 in slightly in the wrong location here so that it does not work when used by Open Orienteering Map.
It should be on the west side pavement of Park Road, not in the private property of the house. It should be moved eastwards towards Park Road.

This marker is in approximately the correct position I believe.

Apologies I haven't spent the time to work out how to correct this myself in OSM. 