Hi Duncan did you actually read the posted reply properly, the guy was offering you alternative means of insurance should your company decline to insure you with the spacers fitted, why dont you ask your existing insurance company if they will accept this modification before going ahead and running in to a wall when they wont do it, most insurance companies view these types of modification very suspiciously as they may well unsettle the cars steering and suspension geometry, each insurance company has its own team of mechanical engineers who assess the possible impact of such changes, you seem to be adamant that you will do this anyway but you have not had the answer you wanted, just sound basic advice which you dont seem to want or pay any attention to, I wish you luck.
Steve.