I recently discovered that Daniel Radcliffe and Emma Watson were Hollywood's highest earning actor and actress, with estimated incomes of $41m and $30m in 2009. I'd always considered them minor stars but now I see that I was wrong.
Your task is to identify all of the following (C and E have already been done for you):
A = Harry's surname
B = Name of Harry's owl
C = Radcliffe
D = JK's surname
E = Hermione
F = Watson's second (nearly 5 years before Hermione)
G = Watson's first (nearly 9 years before Hermione)
It may help if I tell you that F is also the first name of a character at Hogwarts (its just a coincidence).
Once you have identified A to G it will be obvious how to assign numbers to them.
Now calculate the offsets X and Y:
1000*X = A - D/4 - F/3
1000*Y = (2*B+C) - (E+F+G)
Use X and Y to adjust the dummy co-ordinates (X for the westing and Y for the northing) and this will give the location where the cache is hidden.
You can check your answers for this puzzle on Geochecker.com.
Please don't leave any spoilers in your log and have fun.