Apart from the gaps the other things that bothers me is the shape of the petals, they aren't regular. So how to solve this? I ended up doing three things, I went down a needle size, went up from 1.25F to 1.5 F, and put some guide lines in between the petals. I've used yellow couching thread for the guide lines so I can see them while embroidering and can then take them out once the petals are completed.
This process worked very well on the smallest of the flowers so I went onto the larger of the two, well when I say larger this one is about 2.5 cm across.
They also seem to work better working from the centre outwards rather than the other direction, not sure why but it works so I'll continue with this method.
I'm happy now with these chrysanthemums so I'll continue to put in all the basic shapes then will go back and put in all the knots which go over the top. I've only done about a third so far, so quite a bit more to do.