Trying to resolve a sun issue

The presence of the sun is a fundamental part of the first and final shot of the piece.  However, when it came to applying this to an image plane that I assigned to the camera.  I had several issues when I tried rendering it.

There was a lack of both clouds and sun, producing a clean red texture.  I had a go at adjusting both the elevation and azimuth of the sun but this made no difference.  I also tried moving the 'place3dtexture' object that contained the sun but this also made no difference.

Eventually I decided that for these particular shots, the best thing would be to render the sky in a separate file and the scene in another file and then composite them together in AfterEffects.

When I exported it to a video, here was the outcome.  None of the animation has been put in quite yet.

From this, I have found that it is efficient to apply an image plane with an envSky texture to a daytime scene; but when it comes to more complex stuff involving clouds and sun, I will be better off rendering the scene and sky separately and compositing them together as it does not seem to work as well in a scene which already has models placed in it.  I will just need to make sure that both the scene and sky have the same number of frames and are timed against one another.