Sorry to hear it, but I echo what Legal Eagle & SteveScooby say.
Your insurers will pay for repairs under your policy terms, but unless you can prove that the Highways Agency &/or the Police received a report of the debris and then failed to act on it in reasonable time you wont have a case for recovery / compensation. Notwithstanding that, they will say you should have avoided the debris because you should have been driving within the limits of your vision to react to it laying there. Sorry.
