Sark gets a Multi. Not for the first time, surely?
Anyway, at the given co-ords you'll find a historic phonebox. Info here will take you to a plaque & the plaque will get you to the final.
The plaque is at N49° 2A.BBC W002° 2D.EDB where, all on the box below the 'phone', in red:
A= The total number of the letter Os.
B= The number of lines of red text.
C= The number of underlined words.
D= The total number of Ds.
E= The number of words which Aren't underlined.
At the plaque, HPB? You're in the right place. 30.4.19F1-31.1.1976. 19G6-Tenant-1976. 19H6-196J.
The final - and I've not sent you the wrong way - is at:
N49° 2(D+H).(J-B)C((A-G)-(C+F))
W002° 2(H-G).(D+E)(B+F)(J-A)
Good luck & happy hunting! All elements are wheelchair-friendly. T rating is only above 1 due to the distance to roll or stroll. Enjoy.
My other Channel Islands caches:
Alderney: Dear Lyn E (Alderney, CI).
Alderney: It's the Fort that Counts - Alderney.
Alderney: Count the Bright Hours Only... (Alderney, CI).
Alderney: Going Ballistic on Alderney.
Jersey (well, south of): Capt'n Simply's Pirate Booty.
Guernsey: Bridging the Divide (St Sampson/Vale, Guernsey).
Sark: Kars (Sark, CI)
Sark: Hunting on the Sark
Sark: Rings a Bell - Here!
Sark: Peake to Peak.
Herm: Smirfe Hole (Isle of Herm, CI).