Leaking central heating

We seem to have a leak in our central heating system (we are losing pressure) which probably occurred during the cold snap around Christmas. Our plumber has checked most of the joints but as we have just put down reclaimed wooden floors he has been unable to check every pipe. Is there any way of avoiding having to lift the floors? The pipes are a mixture of plastic and copper and it appears that any leak is on the ground floor as nothing has appeared on the ceilings to indicate a leak above. Please help, I think we might cry if we have to lift the lovely new floors.