Like all Michalak's designs, Polepunt isn't specially pretty but it does the job and is easy and cheap to build. The principle is that you assemble the sides on a set of frames, then pin and glue a sheet on the bottom, trim it to shape and there you are. It is only 15ft long but that makes it easier to put on top of the Focus Estate, dunnit?
Wojtek Baginski in Warsaw built one to explore some rugged streams in Poland, and now Graeme Fraser in New Zealand has built one - his report appeared in Duckworks a little while back (the pictures are his).
Some people really can't accept the chine log along the bottom, but it is speedy to build and adds a lot of strength to the hull.
I feel a Wickes special coming on - they sell quarter-inch exterior ply at 16 of our English pounds for a 8x4 sheet, so the whole damn thing could come in at under 100 quid, less if I can use the only-just-out-of-date epoxy I have been given.