They're will probably be a bigger cost for the 'trace and access' of the leak and putting the floor back than to the pipes themselves, so check under that section of your policy to see what is covered. The plumber should be able to do a pressure test to see if you are losing water and they're are also specialist companies that can check for leaks without digging up the floor. Sounds like a significant enough job though so I'd say you will probably have to claim. Their are a number of specialist insurers on the market that will quote the year after you make a claim so if you're existing company quote a crazy premium, you will have options.