Just playing devils advocate here, so bear with me! Was the worktop fitted as per the instruction leaflet that usually comes in the shrink wrapping? Were ALL cut edges sealed? I've fitted some of these in the past and always always take extra care to treat all exposed/ cut/ worked edges with a sealant (usually thinned down polyurethane varnish or PVA). The smallest entry point for moisture can ruin any laminated chipboard. If the bubbling you refer to has occured around the edge of the top (near the wall/ tiling) or around the sink you can be sure that moisture alone is at fault. If this is the case the worktop supplier is not at fault and you'd be best advised to take up his offer and redo the job, it's a pain but doable.