Paper and Is-was sounds a bit obsolete, as that is WW1 "technology".
On the other hand, the brits tended to fire more torps at individual targets than the germans or even the americans, with notable exceptions of "aces" like Wanklyn of the Upholder. A spread of six was commonplace for most larger targets, and their boats where certainly build for firing a lot of torpedoes at once.
With early T-class boats you could fire a spread of 10!
I always noted that british subs tended to be "ambush" weapons of some sort, lurking at choke points and waiting for targets to pass by. Some boats did agressive hunting, but normally they were more or less static.
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