These are not the final co-ordinates.
Start by completing the 5 Lab caches - A Walk Through Ongar. It's a pleasant walk through this lovely and interesting Market town, answering 5 easy questions along the way. On completion of the 5th Lab, the final co-ordinates to this Bonus cache will be revealed - a very short walk away.
Download the free Adventure Lab app. Now look on the map for Ongar. Click on the A Walk Through Ongar symbol and then enjoy the adventure.
The final cache is a film container sized micro in a camoed bag - bring your own pen.