I don’t think this was criminal damage because there was no criminal intent and no intention to cause damage. I would be surprised if the police pursued it but if they do, all well and good. It was almost certainly negligent and reckless.
Whoever lit the fire is responsible for the damage and in my opinion the tenant of the ground for flat that had the party is jointly liable along with whoever did it for the cost of that damage.
Although I would like to say that I think the landlord is responsible also for allowing this, I don’t think it’s reasonably foreseeable that the damage would be caused in the way was by his tenant so I think a claim against the landlord is unlikely to succeed in respect of the damage.
If the tenant won’t pay up and and nor will the fire lighter than you cannot beat them with a stick until they do and your only remedy is to issue Small Claims Court proceedings against them and let a court judge decide the matter.
At this stage in time, you need to get a couple of quotations for repairing the damage and present those to the tenant of the downstairs flat and give her 14 days to pay and if you have been paid, don’t mess about, issue Small Claims Court proceedings which you can do quite easily here www.moneyclaim.gov.uk
Can I clarify anything else for you?
I’m happy to answer any specific points arising from this.
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