Hi Ken,
Which Midget are you referring to as Mk1? There is the pre war Midget and then the Mk 2 & Mk3 came out post war. The Atco Villiers is sometimes referred as the Mk1. If this is the engine that you are interested in there is no actual manual for it that I have been able to find. The majority of the settings such as timing, carburettor settings etc are in the Atco instruction books for the models fitted with this engine.
Cheers,
Sir Chook