Bashibazouk

Yes, I do, a ton of mods installed. And very messily installed as well, I'm afraid. I'm trying some other stuff (modification of the XX:\Eagle Dynamics\DCS World OpenBeta\Bazar\shaders\model\functions\glass.hlsl file) , I'll come back and report my findings.
OK, commenting out the lines (88 and 89 in the current build) - 
 
    if(!(Flags & F_DISABLE_SHADOWMAP))   //two lines - 88 and 89 commented out to remove F1 canopy whiteout
         shadow = min(shadow, applyShadow(float4(mp.pos, input.projPos.z/input.projPos.w), mp.normal, true, true, Flags & F_IN_COCKPIT));
 
Fixes the whiteout problem. It removes any reflections, from what I can see, but the F-1 is currently my favourite plane so I'll live with that. No doubt the next update will reinstate those two lines, so hopefully whatever interaction is causing this will be gone by then, otherwise it's back to Brackets (or whatever the replacement for Brackets is called, I can't remember off the top of my head!)/
 
Correction, it doesn' t kill all reflections. Just the bad ones! I'm not gonna investigate further, I do that sort of stuff at work, I'm on smoko 😄 https://www.youtube.com/watch?v=j58V2vC9EPc
Nope. Still no good.

Ok, yes. It is a senior moment. Because I set a  steer/target point with the Mav bore sighting, the tadpole, quite rightly pointed towards that. As soon as I set the TGP to the steerpoint, everything fixed.
D'oh. I'm only leaving this embarrassing thread in case it happens to anyone else!
 
Full steam ahead and as you were, support team. Weasels Over Syria, here we come!