Oh, they're there allright. apart from in the convoys there's several fairly regular taskforce-routes, these vary per time-period but they're consistent for at least 3 months or so
in 1939 and early 1940 AM36 and everything north of Scotland and West of Scapa Flow is a good place to find BBs
In 1940-1941 you'll find them transiting from Scapa, round the back of ireland to Gibraltar fairly regularly
from late 1940 to 1943 the med is also a good place to find BBs especially around Malta
After that I wouldn't go looking for task-forces of any kind because the DDs will kill you for your insolence
I'm being not too specific here because I wouldn't want to spoil all the fun of discovery
happy hunting
