Note as of 15-01-2023. The posts at the start point have been vandalised, and one sign has been ripped off. The values are now the number of nails affixing the remaining 5 signs PLUS 4
Orienteering is a competitive sport involving navigating from point to point at speed in challenging terrain using a specially prepared orienteering map, and sometimes a compass. The maps are smaller scale than OS maps, and contain a lot more information, so take a huge amount of time to survey and prepare. In many respects orienteering has lots of similarities with Geocaching.
This cache is a multi which uses a basic style orienteering map to navigate the paths round the woods to find the six control points, and collect the 15 letters required to find the cache. The letter code information is on metal dog tags hidden as per the clues for each control point (The number next to the letters is just the control number). The published coordinates are for the start point, which are a pair of wooden posts on a path junction, here you need to collect the key for the puzzle, the values of X and Y.
How many nails affix the 5 remaining round signs to the posts? PLUS 4 = XY?
From here on GPS devices and phones should not be used until finding the actual cache container, unless you get hopelessly lost and need a reset! You will find a print out of the map a lot easier to follow than trying this on a phone, and you can mark where you have been to aid navigation. All the controls are close to paths, so no need to go a long way off-piste bushwhacking as you might do in an orienteering competition. Note the attributes with respect to the cache container hide, although you may pefer to access it with a special tool, which you will find plenty lying on the ground.
Whilst the marked paths on the map are accurate, there are the odd one or two extra paths that have appeared as short cuts or diversions. These woods are complicted, which is why I chose this area as a good test of navigation skills.
To add a little competitive edge, you may like to add the time taken in your log. Have fun! 
Click on this map, save it, then print it off. (The one in the gallery appears to have been compressed, and is smaller)
Start Point. Pair of wooden posts. How many nails affixing 5 signs PLUS 4 = XY
Control 1. Medium beech up bank, attached to root at base facing the path. Rotate cable to reveal the tag.
Control 2. Medium pine, 8 feet out on second live branch up.
Control 3. Behind top of log bench, left of centre.
Control 4. Large knobbly beech, 4 feet up, 3 feet out, on small branch pointing up the valley.
Control 5. Small twisted beech, 2 feet up, left hand side.
Control 6. Medium fuzzy beech, 4 feet up on small branch opposite side to gully.
Spoiler pictures have been added to the gallery if you need extra hints.
The coordinates for the cache need to be unlocked using the key XY. Using a simple 'ROT' cipher which rotates the whole alphabet a number of steps in either a positive or negative rotation, eg +ROT 4 for the letter A is E, and -ROT 3 for the letter G is D (online solvers may get you in a mess!)
Controls 1 & 2 (5 letters) +ROT X
Controls 3 & 4 (5 letters) -ROT Y
Controls 5 & 6 first letter +ROT (X+Y)
Controls 5 & 6 second letter -ROT (X-Y)
Controls 5 & 6 third letter +ROT (XxY)
Controls 5 & 6 fourth letter -ROT (X/Y)
Controls 5 & 6 fifth letter +ROT ((X+Y)+(XxY))
You should now have 3 recognisable words, if stuck then look at the hint!
Congratulations to the Liberal Giraffe team for the FTF!