The Brit East Coast is a nice hunting ground for the first several months of the war.
but i strongly caution you, several U-boats have been lost to mines in those very areas as early as Spring/summer of 1940... maybe earlier.
the Brits stopped making so many mistakes in that area fairly early on.
traffic in the area was reduced, and more escorts were assigned the area as they became available, but the biggest threat is the shallow water and the mines.
if you get pinned down by ASDIC you have virtually no place to escape to
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