The key element in CAS in the early war was the US Navy Corsair. If you can source the 1/144 kit its around £4 plus postage on ebay. Then I discovered the Irregular Miniatures version at £1.60. Now its in 1/150 so is noticeably smaller than its 1/144 cousins ( all Ian Kay's ranges of 10mm- are more like the old War Games South neo-N gauge in stature). But I have to say its a neat sculpt and captures the little fighter bomber. And at £1.60 won't break the budget.
I might even model one in a crashed base, and you could have a mission extracting the pilot.....
Cheers
James