Storm and Assault Boats

[John Sliz]

Here is a challenge! If anyone can solve this mystery, I'll be amazed - and extremely grateful!
Stormboats in WW2 were made by both the U.S. and the U.K.
The American boats were smaller, while the British boats were 20' long and could take loads such as a 6 pdr AT gun. Where were the British boats made and how many were made during the war? Any idea if the plans of these boats still exist? I would love to get a hold of the plans!!! I know someone who wants to reproduce a Storm boat.