From the inital coordinates, or indeed any corner of this intersection, you should soon spot a feature that will help you work out the coordinates. If in doubt take a little walk. For W you only need the final digit of the number.
The South coordinates are:
NW, W N,N. WNW, WNW, WNW
The East coordinates are:
WNW, WNW, ESE E, W. NNW, S, E
The cache is only a short walk away. Watch out for muggles as this is a popular walk through area to the shops. PLease ensure the cache is hidden when you replace it.