he should get an independent engineer to look at it, and contest there findings.
i had huge problems with highway insurance when someone ran into the back of me.
they stripped me of my no claims for 9 months even though the accident werent my fault, and they said it was because i made a claim, i did make a claim but the accident werent my fault so it shouldnt affect my no claims.
in the end they said they were waiting for the other guys insurance to pay them there money back before they give me my no claims.
i fought tooth and nail to get it sorted and phoned them 3 times a week until it got sorted, and in the mean time my insurance ran out and i had to get a policy elsewhere and pay an obscene ammount, lucky the new insurance company were very helpful and when i got my no claims back they reimbursed me the extra money i had to pay within 1week.