Thank you for posting these fascinating images. I’m pretty sure those are either modernised S, or perhaps, T Class WW2 submarines. In the 1950s some were stripped back for high speed tests. They seemed to have conning towers similar to the German Type xxi boats. The conning tower.on the dock, for instance, perhaps from an earlier boat, has a roughly painted pennant number S14, which was HMS Supreme but was passed on to the Oberon class boat, HMS Onslaught, still in service when you took these. However, I think Supreme was scrapped 35 years before your visit. This is really interesting and I wish you good luck with your research. Please let us know what you find out.