There's one complete Model 18 for sale, a 1930 bike that looks quite correct; John has taken the gearbox to bits to "try and find out what the differences are inside the Sturmey boxes... There ain´t not that many lads in my area that knows about hem boxes. What a nightmare of fun it has been". The Model 18 is said to be complete. Click this link for many more pictures of this bike.
Another complete Norton SOLD
Finally, there's a huge load of 1920s parts. I've seen Enfield hubs, sprockets, Druid girders, Best and Lloyd oilpumps, Sturmey-Archer parts and much more. Click this link for and album of pictures of the spare parts
There's much more than in the pics; contact John directly at firstname.lastname@example.org (note the spelling of notron!)