This is Number 14 in the 'Fine Pair' series, where a red telephone box can be found within 20 feet of a red post box.
The cache is not at the given coordinates.
To find the cache, look in the phone box and note the number. Excluding the STD code, this number is ABCDEF
Go to the post box and note down its number starting BN. This number is GHJKLM
The cache can be found at N50 (D+E)C.EK(M-(G+J)) W000 EJ.(M-L)HA
If anybody would like to place 'A Fine Pair' of their own please do, I would just ask that you could let wizardsmum know first so she can keep track of the numbers and names to avoid duplication