Anyone for Tennis? Mystery Cache

I have to admit this puzzle is almost a direct copy, in style, of one to be found somewhere west of here, obviously I can't say which puzzle. Confession over, let's get down to it.

Usual story, not to be found at published coords - 10s are 0s.
Absolutely no clues or help for this one, there are hints galore.

In order to solve this puzzle you need to discover who A is, B C and D may help you. A created something linked to E and F. That something and G to R will give you some coordinates.

N 51° MQ.NJ(R-O-K)
E 000° (I-L+Q)G.(N-J-Q)PH

You can check your answers for this puzzle on Geochecker.com.