On the M25 you take exit 10 and you go over the A3 towards London. Then take the first exit towards Cobham (A245).
Follow the A245 (towards Leatherhead) and after a viaduct over a railway you are at Stoke d'Abernon.
On a hill on the LHS you see a big telecom mast. The NDB is near this mast.
There is a path along some houses, I'm not sure if this is a public footpath.
About 500 metres further along the road we found a path to a barn. From here a nice path led to the top of the hill.