Bodged conservatory floor

We had our conservatory built a few weeks ago.
Because I had to wait ages for a plasterer to turn up, I have left the floor as it is and plan to lay laminate flooring when the rest is finished.
Over the last few weeks, as we have walked over the floor, the surface has gradually deteriorated - there is an area near the door where the gravel in the concrete is starting to crumble out (although it's only on the surface.
I think the problem has arisen, because when they did the floor, they used readymix concrete. However, there wasn't enough, so the 'builders' mixed some concrete themselves to finish the job off. It seems as though they didn't have enouh cement for the mix.
I have contatcted the conservatory company about this. After quite a few days, they got the contractor who did the floor to call me. He said he would pop round and put self levelling compound on the floor to sort it out.
He didn't turn up to do the job.
Someone else has also told me that I can fix this with self-levelling compound (and sealing it beforehand with PVA).
I have the following questions:
1) Is self-levelling compound good enough for the job?
2) Is there a body such as trading standards who I can threaten the conservatory company with? Is it possible to get them to come and look at it to give me some advice.
Any advice would be greatly appreciated.
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