You are unlikely to get a solicitor to take this on a no win no fee basis. Hence, you will be faced with dealing with any litigation yourself.
You are entitled to recover any loss caused by negligence. Clearly, there has been some failure to repair here and hence, your shoes if they are damaged.
In the absence of a receipt for the shoes, you would be entitled to produce evidence of how much they cost and the shoes themselves, if this got caught.
Being blunt with you, if they have offered you €200, my advice to you would be to accept it. I know that you have turned it down but the alternative is to issue legal proceedings against the airport in Paris which might not be particularly practical for you.
With regard to your daughter no longer wanting to go to the toilet at the airport because of the previous experience, I’m afraid that it is unlikely you would have a claim to make in respect because it is probable that a judge, if this got to court, would say that any ongoing incidences would be too remote and not reasonably foreseeable. It is not reasonably foreseeable that if the airport doesn’t clean the toilet in Paris, that your daughter would refuse to go to a toilet in Cardiff.
I’m sorry, I wish I could give you a more favourable answer but that is what will happen here.
Can I clarify anything for you? Please rate the service positive so that I get paid. We can still exchange emails. Best wishes. FES.