[Moggy]

I don't think it really matters but in the Hurricane Mk.I pilot notes it does state that before the engine has started the fuel distributor switch (another word here) should be turned to reserve. As soon as the engine has started, switch off the starting magneto. Turn the fuel distributor switch to the "Main Tanks" position to test the engine fuel pumps for satisfactory working. After take off, the fuel distributor switch should be moved to "Main Tanks".
However with this being said, it does say you can take off using the main tank, so that's why I don't think it's too important. But before starting it should be using the reserve tank as this will use gravity feed and the main tanks are below the level of the engine.
Interestingly enough, in the Hurricane Mk.II start ups are made from the main tank. So something changed inbetween.