The cache is not at the published coordinates. Solve the Code Cracker and you'll be halfway to finding exactly where it is.
This puzzle has been reproduced with kind permission of Simon Shuker.
The cache can be found at S41 1S.TUV E173 0W.XYZ
Where S = Q minus C W = A plus D
T = D plus M X = F plus G
U = F minus E Y = F minus C
V = G minus E Z = B plus I
Please be discrete when searching for the cache. The presence of some people might be obvious but there could also be people watching from afar.
Sorry but there is no room for trackables in the cache and you will need your own pen or pencil.
You can validate your puzzle solution with certitude.