The co-ordinates above are not for the cache, the cache can be found by completing the "Crookham Park and Ewshot" Adventure Lab series.
You can find further detail about the smartphone app for Adventure Labs here: https://labs.geocaching.com. If you already have the app then search on nearby Adventures to find "Crookham Park and Ewshot". The whole Adventure and this bonus cache should take you around an hour to complete.
The coordinates for this physical cache will be revealed after you have visited and answered a question at all five locations of the Adventure Lab series. Once you have completed all sections of the Adventure, open the “View Journal” section of the Adventure and use the following:
N 51° (B*A).C(A+B)D ' W 0° BD.(C*2)EB
Free parking is available either at the community centre or in the Naishes Lane SANGS carpark