At the Coordinates above is a large carved wooden bench. This is at the start of the North Downs Way.
On the bench there are some engraved distances. How many Kilometers is it to Dover? This is ABC. Then with your GPS take a waypoint of your current location. You will also need to find the value of "X" on the bench. Make sure you search high and low.
Next walk to the to the other end of the North Downs Way, where there is a similar bench at N51 06.765 E001 17.790. It is quite a long way, but you should be able to walk there and back in 6 days - maybe just 4 days if you walk really quickly. Now how far is it, in Statute Miles and as the crow flies, back to the waypoint your recorded at the bench at the Farnham end? This is DE.F
The cache can then be found at :
G = A + B + E - C
X = ?
N51 G A . D [X – C] G W000 B [C + G] . C [X + A] B
Good luck and I hope the walk there and back wasn't too tiring!