Appears to have a Lucas K2F magneto.....
This was one of my thoughts, John. Not sure when the Lucas K2F came out, but the flange-mount BTH didn't appear until 1933.
Another thing - which you mentioned earlier - is the enclosed valves. Nothing at all like that in 1930?
Also I wonder when the script Villiers logo - with the top of the V forming an oval - was first used. Maybe on the primary cover of the 8D/9D in the mid 1930s? Was it around in Villiers literature in 1930?
Re patents: there was very little to patent about the parallel twin by the time Val Page then Turner did their work in the 1930s. Most engine configurations had been tried by this stage, parallel twins from the early 1900s, and if a design was already in the public domain there was no way to patent it.
My theory: This Villiers engine is not 1930. (Are we sure the 1930 Villiers 500cc twin was a four stroke, and not a 500cc version of the Pullman two-stroke twin rotated through 90 degrees?) Could be late 1930s, could be 1950. Could it be even later - some kind of universal engine for NVT? With a single Villiers carb, could it be for a non-motorcycle application? Maybe a military contract?
Cheers
Leon