Dave,
You're quite ahead of me and I am trying to find based on your experience where I can go wrong. I don't see the problem with the coaming in my version it almost slides automatically over the cockpit:

It clicks over the fuel caps and I don't have any problem with the MG supports. You might discover on the other hand what I did wrong. The magazine box is tilted slightly forward, which leans in front on the edge on the coaming too much and results in a not exact fit of the bullit belts into the Spandaus. It can probably easily be avoided in taking a little bit more care with glueing the empty belt box and the magazine box together. At least that is where I think I made the mistake.
The fit of the coaming however is not completely snug to the fuselage halves:

Nothing is fixed here in this picture. The fuselage is slightly opened at the front, but will close to the pieces of the firewall, which are marked inside the fuselage halve. Also the coaming can be pushed gently in the correct position, thus resulting in the required fit.
I haven't progressed to the engine panels yet. I read at modelling madness that Tom Cleaver ran into problems here too. I do find just as you did that the radiator doesn't fit very well to the chin cowl:

I have already tried some filing at the outer edges of the chin cowl, but it doesn't really help. After painting you might not notice it this strong, also because at the real thing they were all separate parts.
Hope to see more of your progress.
regards,
Ivo