Supermatt is suitable as a finish paint, but, as it is non vinyl, does tend to have a slightly chalky texture, so I only ever use it for misting.
I think your problem might be the fact that you are using the Crown, which is a non vinyl paint (assuming it's the one I'm thinking of) and trying to blend it in with the rest of the ceiling which could possibly be finished with a vinyl. Don't know if that is the case
, but if it is, even if you do the whole ceiling with the Crown paint, the patched area will still be noticeable until it too has had a coat of vinyl.
The best paints for hiding power in your situation are the trade version vinyls, but, as you know, they are more expensive.
There is nothing wrong with the Crown paint you are using from Q&B, and as a decorator I've used loads of it, but it just doesn't have the hiding power for the situation I have described above.