I did a few years in the Jaguar tank bay.
Our 1200 litre tanks were made of Asbestos / phenolic resin. They were three parts, with the centre containing a large cast suspension beam. Inside, there were baffles at the front and rear of the centre section, with a high and low level float valve to say when it was full or empty.
The tanks were pressurised to provide a pressure fuel feed to the aircraft - not sure about the transfer system - I'd have to dig some notes out as once on the aircraft that was more the sooties job.
We'd normally get them in for dodgy float valves, sometimes for leaks, or if it was one of the war reserve tanks then just for periodic maintenance. All this was done by the airframe trades on the Jag, with suitable sign offs for minor electrical work.