The puffers were built to the VIC design mostly between the wars though I know of one built on the Thames which was built during the war because they were cheap didn't use fuel oil and were easy to maintain. The Thames one I know of (VIC145?) generally lies at the Chatham Historic Dockyard. There's another in the Greenwich Museum and three, all called "The Vital Spark", are at Inveraray, Crinan and Ardrishaig.

While the hulls are to a standard design the superstructures vary enormously. The funnel can be in front of or behind the wheelhouse, which can be square or six sided. I think windows rather than portholes because they were often on canals and shelter is never far way on the West Coast and the Thames estuary and the East Coast are equally easy even though the mud and sandbanks do force a boat further off.

There are plenty of pictures available on the internet.

Archie