If Ubi ever added a British boat expansion/game, everyone would have to really hone up on their targeting by eye.

IIRC, British boats had a very rudimentary torpedo aiming device. Nothing even close to the German or American TDC's. Might make it pretty frustrating for the casual gamer and auto-targeting option would be needed and waaaaay too accurate.
I would love to see a campaign add on with British boats in the Med though(I don't think there would be enough there for a stand alone game). I think it would be quite the challenge, especially if the subs are modeled realistically to present some of the challenges they faced-torpedo aiming, depth keeping problems after a torpedo was fired(I've read a few accounts of British boats broaching after firing torpedoes).