Yup, my car failed the NCT (National Car Test) today. Couple of things were wrong, brake bulb (easily fixed), headlights not properly secured (had them out fixing the rad, not a problem), now the last problem is odd, cracks in the sills, nearside/offside, this is aroun where the car is jacked up, when changing tire. The mechanic recommended some putty, but I don't fancy that. What are the options? Grind down, filler? or spray it with an underbody spray to cover the cracks, or is there a possibility if I don't fix this prob now it will rust and I'll have a major prob. Its a 10yr old MKIV 20V Turbo. Advice?