The surface surrounding the bunker has changed considerably since the War. One of the major changes was the dismantling of the many Nissen Huts and water tanks that existed in the early 1940's. The other was the erection of the DSS buildings in 1948 to house offices of the fledgling National Health Service.
The area actually on top did used to contain many shrubs and trees (as can be seen from the map) though today it is just grassed over. There is still some greenery that exists on the south side around the concrete mast plinths.
The bunker had two main entrances/exits, on the west and east side for obvious reasons (in case of attack, fire etc.).
The map below shows the site in 1948, as it was at the time.