The second cache in the Felix rebound series - see #01 Felix rebound for more details.
I have had fairly variable satellite reception under the trees. If you want to use the hint you will probably find it specific enough.
You are looking for small camouflaged film canister.
Before you leave here you will probably be aware that the land owner has spent some time highlighting the correct footpath. I have been down here and done some gardening to try to improve it but you may still find it rather overgrown - mind the brambles! Alternatively, use the much better path at the edge of the field.