Last year I had the sills resprayed and fitted mud flaps (or Splashguards in current Jaguarspeak). After a few months I began to detect the return of this rash but much reduced from the original level of attack. I have not heard of the splash plates that Ray mentions but I do know that several owners have fitted clear paint protection film as an effective barrier to stone chips.
How long it lasts and whether it may cause paint damage when removed I don't know. Perhaps a member has some experience with this film

