Yerss, my mate has one sitting in his shed that someone had dreams of turning into a road racer!!(It's worth two exclamation marks just to think about it.)
Basically what do you want to know? Mechanically it is just another Villiers lightweight built to the standard formula of Villiers 9D engine, pressed steel Webb forks, British Hub Co wheels, etc,etc. About the only thing that distinguishes it is the monster cast alloy silencer hanging in front of the engine.
If you can get hold of a copy of Roy Bacons "The A-Z of British Motorcycles from the 1930's, 1940's, 1950's" you will find a nice photo of it on page 272, plus there is a little blurb on Montgomery (with pictures) on page 154.
Obviously as it is made up from all proprietary parts there is no point in looking for a factory workshop manual, all you do is get the relevant Villiers etc, material and go from there.
It's a simple restoration but one that has to be spot on mechanically if you want an effective bike to rally. These bikes didn't have a huge performance when new so anything not quite right in the restoration quickly becomes obvious on the road.
Oh, last thing, it's a Montgomery 'Terrier' and 1940 was last year of production.
Cheers,