I have never had to make a claim, but I should imagine that its like any other claim where you ring the number provided and they offer you their own suppliers or you designate your own.
Just like any other type of insurance, I imagine you cross your fingers and hope for the best.
If it’s any help, the installation process doesn’t need for any roof removal. 7000.000 installations and rising in the UK alone can’t be wrong.
Welcome to the brighter side of the force.