Martins in Britain are sold with a disclaimer that Martin is not responsible. I.e. no lifetime warranty just normal sale of goods act and suchlike.

I've an idea that disclaimers like that aren't necessarily valid. And the sales of goods act would mean that the person it was bought it from carries some kind of legal responsibility. They sold it as a instrument in good condition, and I would have thought that this kind of damage so soon after buying it would mean it wasn't fit for the purpose it was purchased for.

If the suggestion was that the damage was down to your friend's treatment of it, they might have an out - but if they are saying it was because of the way it had been treated by the person from whom they obtained it, they would be fully liable, I'd have thought. (They might have a claim agains the previous importer, but that's their problem.)

Youir friends need to get advice from someone who knows the ins and out of the law on these matters. The local Citizens Rights Bureau might be able to advise.