Phill do you keep the car covered up out side? i have had the roof of one of my old cars do the same after i covered it up for the winter. The car swets and blisters the laquer. If you can try and get it inside with heaters i ended up having to get my roof painted, but my mate had the same problem and put the car inside for a few days with heaters and most of the blisters disapeared.