Calm down guys, the guy simply asked a question about how mixture works, not what went wrong with CoD development
To answer in short:
Mixture controls are semi-automatic in the spitfire (auto rich and auto lean, not full rich/lean but automatically maintaining the best rich or lean ratio), with rich being levers back and lean levers forward.
The should be the same in the Hurricane, but it seems they are manual (full leaning over the entire course of the lever's movement range).
They are correct in the Blenheim, the levers move throughout the entire range (like the Hurricane) but in truth anything lower than 50% is auto rich and anything higher is auto lean. This corresponds to the manual for the aircraft and it was that way in reality.