The Sucrof is the most famous of those seized. As far as I know it was the only Brit captured sub that achieved operational status with the Brits or Free French. It was used to deliver some soldiers to seize a pair of tiny French island off Newfoundland & then was dispatched to the S Pacific, to the French colonies there, after a extensive refit in a US naval yard. So after its capture in June 1940, with a trained/experienced French crew, it managed maybe two combat missions, a Atlantic transit, and a transit to its wreck in the Carribean. That suggsts something of the difficulty in using such a vessel without its support structure ashore.