Best nearby parking is on Old Lane. From there, just follow your GPS. It's about 20 minutes to walk from the parking to the cache.
The cache is set near an interesting relic of naval communications history. In 1822, messages were sent between London and Portsmouth in just 15 minutes, and Chatley Heath is the last surviving tower in the chain. In the tower, now converted into a museum, you can see demonstrations of the working semaphore mast and have a go yourself on replica models. The museum has really random open hours. It used to be open one week-end an month but this is apparently no longer the case. Up-to-date information can be obtained from the Surrey Wildlife Trust web site.
Geocachers in a hurry can park closer, on the other side of the M25, but frankly it's a shame, as the walk through the heath is really nice. As a bonus for the walkers, the month before Christmas there is a decorated pine tree set up on the way.