Codes Mystery Cache

This cache was placed during a trip to this excellent area. We like puzzle caches but the nearest one was over 500km drive away. So we decided to create one here.

The cache is not at the posted coordinates. There is no need to go there.

It used to be the location of the visitor centre but that has now moved. There is no need to go there either unless you want to check out local things to do!

The Puzzle:

Use SENIOR ROYAL AUSTRALIAN NAVY WARSHIPS OFFICER 1770 to create a string of digits represented by the letters from A to P inclusive.

Replace the letters below with the appropriate digits from the string to find the location where the geocache is hidden. 

South 21º 5G.D(F-H)(B+N) East 114º 0P.ML(I+A)

BODMAS does not apply.

Note: The physical cache is kindly being maintained by Tonno87 - with many thanks B&J

MoM Note: If you are trying to solve this for the MoM please do NOT message the previous finders. There have been multiple messages to all finders and the CO since this one was added. It is not an easy puzzle especially for non-Australians but it is solvable. If you do need a hint please message us as the CO with what you have tried so far to show you have made an effort, and we will try to give you a further hint. If we are travelling ourselves there may be delays in answering, but we will definitely answer when we have internet access.