As I say, add the HACS directors from the RN sheet. As for a mast, look at:
http://www.shipbucket.com/images.php?di ... rd1946.png
Lookie, tripod masts. Those are pretty standard for post-WW1 british BB's.
Edit: No, you put the directors on the super-structure, one fore and one aft. look at Vanguard above.