Obtaining the final coordinates for this Letterbox should not be too much of a challenge, if you know what you are doing. Firstly, you will need to head to the PO Boxes, which can be found very close to the listed coordinates. From the listed coordinates, you will need to head towards the entrance (that is just a few meters away) that will take you into the shopping complex. Once you are undercover (before you would walk through the door), you will immediately see the PO Boxes on your right.
Firstly, you need to find the four numbers written on the PO box in the top left-hand corner of the ‘grid’. These, read left to right, make up ‘ABCD’.
The other numbers that you need can be found on the PO Box that is in the fifth row from the top and the fifteenth box from the left (hint: it is one box to the right of 1075); these numbers, read left to right, make up ‘EFGH’.
With these numbers in hand, you will need to apply them to the offset formula for the final coordinates. However, this formula will not be found of the cache page and, to find it, you will need to look elsewhere.
Stealth may be needed at both the listed coordinates, and the final, as they can sometimes be high muggle traffic areas. Also, the stamp in the cache is not a tradable item and should therefore be left in the cache.