[NikToo]

Don't know what all the confusion is about over this. The British medal system is quite clear. For the Royal Air Force in 1940 the awards would simply have been:

VC: Officers and ORs. Obviously very rare.
DSO: Officers, for "distinguished service".
DFC: Officers and WOs, for "valor in [...] active operations.
DFM: NCOs and ORs for "active operations".
MID: Mention in Dispatches, which wouldn't lead to an award per se until the end of the war.

Quotes are from the Medal Yearbook, 2007 edition.

Bars would be added for additional awards. Note that DSOs, DFCs, and DFMs could also be given out at the end of operational tours, noting basically the bravery it took to do a large number of missions rather than just a single act.

No Campaign Stars were awarded until after the war. However, it was possible to wear the ribbon for the 1939-43 Star along with the Africa Star ribbon after 1943. Only the ribbon was awarded, not the Stars. Of course, this was later amended to the 1939-45 Star.

So in the terms of a game do really well in a mission on an easy setting and you get the DFM, finish a campaign and get a bar. On a difficult setting the DFC for a mission and the DSO for a campaign or a bar. One thing to remember is that you can't exactly mimic life here. After all, it only takes about five kills to become an "ace", but it would be a pretty boring game if you really had to struggle to just shoot down five aircraft. Most people probably approach Marseille-like numbers quite easily.