Looking good Lewis.
Have you done anything to the diffraction spikes, or is that just how they come from your system? They look quite heavy very close the the star.
M42 can always be a challenge... if you want to take it up, try stacking some different exposures to try to get the trapezium to pop out without losing the detail in the darker nebulae (or a bit of HDR).
The full mosaic of Orion sounds like a worthy project!
Al.