caravan insurance damaged shower tray part 2

A few months ago I managed to damage our caravan shower tray when I stumbled into it and put my foot down heavily directly onto the tray and managed to cause a split or crack in the plastic. The plastic seems very thin and we now have to start with a caravan insurance claim.

Not our photo but the damage looks like this

We are insured with the caravan club which is called Club Care Insurance Services.
We phoned them up and asked them how to claim and they advised that would send us a claims form and to try and get 3 independent quotes. We then spent hours on the phone trying to explain to various caravan specialists what kind or type of shower tray we had. Only 1 came to view it and suck air through his teeth and tell us how hard it is to get them out and replace. The other 2 needed our caravan chassis number. 1 quoted for labour only but not parts. I'm not sure which it was but one quote was over £800 and the cheapest was £350 (this was quoted as 4 hours at £25 per hour plus the shower tray itself). A big difference.
All in all, it was a minefield.
After a week we wondered why we hadn't had a response from the insurance company. This was because we hadn't posted it yet and found the envelope in a drawer waiting for a stamp. After we posted it, we had a response within 2 days saying that an independent assessor would be in touch to inspect the damage and to decide if they can authorise the claim.

So that's it so far.
to be continued......
The insurance assessor came to visit our caravan today and seemed to agree that we can make the claim.
Just waiting for the letter from the insurance company now.

The  letter finally arrived after we phoned and asked why it was taking so long.
They say that they will not pay out because it is a manufacturing defect.
So if you accidentally damage something that you think is insured then they can just say it was always going to break because it was made badly in the first place. so 8 years of use and no problem, but an accidental trip and they can say it's not there risk!
What can I do now? Maybe ask for a list of other items they will never cover because they are prone to manufacturing defects?
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