text: Looking at the map more closely, I see we have a helipad mapped about 40m to the west, and that corresponds to an obvious (H) circle painted on the ground and visible in the aerial view at https://www.openstreetmap.org/edit#map=19/51.46934/-0.17809. There's more information at https://www.londonheliport.co.uk/ which might help to map it properly.