It’s simple really, I made a mistake in transferring markings from my draft pattern to the garment pattern.
I’m not sure if it’s obvious from here but the side front pattern piece should have followed the red line and not the original pencil line (which I had even scribbled out !) I stupidly made my pattern piece from the original outline which meant I had approx 3 cm more fabric in the centre front than the side front. This accounted for the difficulty I had easing in along the seam and in fact was extremely impressed that I had actually managed to achieve this under the circumstances. The resultant mismatch between the pieces pulled the whole bodice out of shape. Once this had been identified as the source of the problem it was back to work to make the pattern piece correctly.
The bit with the scribbles on is the original and wrong piece, so you can clearly see my error.
I then made up two new side fronts in calico and re-inserted them. The garment looks even more terrible now but it fits beautifully !! Thank goodness for my tutor who spotted what was wrong very quickly AND made me put it right.
All I need to do now is source some fabric I actually like and give this another go.