These places that you have to work out are all places I've either worked,or visited in other capacities.
You are looking for a nano container, in a quiet location.
To make this easier, label the co ordinates AB CD.EFG H J.KLM, so no letter i, what you must do is work out what or where I'm describing, and pin point roughly the middle of building or area, it's easier than it sounds, honestly.
A = You may walk like an Egyptian here, E plus 2
B= Good place to roller skate and skate board etc, E plus 1
C= Where the hovercraft actually lands, not a helipad or a lily pad, D plus 2
D= Play up Pompey, J
E= Killer, Humpback, Blue. Island, the field on middle, K divide by 2
F= A big tall tourist attraction in Gunwharf, K
Now you have the numbers, use this equation...N50 46.ABC W1 4.DEF
This should be easy to do, but any problems don't hesitate to message me.