Hi ink,
Great job. I love shark mouthed P-40s. I haven't done any skinning in AH for a while but I keep an eye on the new models coming out and the P-40 series has me opening up my books again.
Just thought I'd point out a couple of things as a self-proclaimed markings nerd...

These aircraft would have been painted by Curtiss before delivery using American 'equivalent' colours to those specified by the RAF/Air Ministry, namely:
DuPont 71-009 Dark Earth (redder than the RAF's Dark Earth) and DuPont 71-013 Dark Green (bluer than the RAF's Dark Green) over DuPont 71-021 Sky Grey under surfaces. There were some P-40s in the AN serial block that had the under sides painted in US Light Blue 27, as also seen on some of the first Wildcats sent to the Med/N. Africa. Google these colours for appropriate RGB numbers to give you an idea. Keep in mind that it is open to argument whether any digital samples you find online are correct, or just closest possible approximations. Artistic license enters here

At any rate your choice of Azure Blue is correct for the time period as 112 Squadron started repainting in Azure Blue by the end of 1941.
The dark boxed area around the aircraft serial number should be green, not brown. The DuPont Dark Green portions of the camo would have been over sprayed in either Light Earth or Midstone once the aircraft left the Nile basin and started operating in the Western Desert. The serial blocks were masked before the over spray so anything located on a sandy coloured bit would have been green originally.
Markings would have been applied before delivery and RAF markings on P-40s were as such (I am giving you the ball park location, the actual finishing instructions would show actual measurements in inches from a set reference point for the center of each marking. ie: so many inches inboard of wing tip and so many inches aft from leading edge of wing...):
Upper wing 48" in diameter, centered fore and aft, with the inboard edge of the blue disc lying along an imaginary line running forwards from the inside front corner of the aileron.
Fuselage 35" in diameter as per the photo.
Lower wing 45" diameter, trailing edge at aileron hinge (see period photo), and moved inboard so it's centered with the aileron. The landing light will end up in the blue portion of the marking on the left wing.
Fin flash is 24" wide (8" stripes) by 27" high, trailing edge of blue stripe lined up at gap between fin and rudder and base of marking along bottom of fin.
Again, these are the "Standard" placements, period photos will always have the last say.
Your under wing roundels look as though they have a slight white outline, did you use a pre-made marking sheet like Simmer's Paintshop has or did you make your own markings? I make my own RAF roundels for every aircraft type (different types used different diameters on wings) as resizing pre-made ones doesn't give you as sharp a marking. I can show you how to do it, just shoot me a PM. As for marking colours,
most of the BS 381C paint numbers as used by the RAF in WW2 do not exist on the modern colour charts today so usually any reference to a Federal Standards equivalent is only a "closest match", not an actual match, so use your best judgement