I use 3M wet type silicone spray to keep the dash from cracking, and then 303 Aerospace Protectant for UV protection. The silicone spray works ... my dad has owned a few MG's for many years and never had any dash cracks. If you use it on a cracked dash, it will stop new cracks from forming. You still need to drill the ends of existing cracks or they will travel over time.
