I've got some time on the Hawker with the TKS system. Both Hawker-Siddeley and FSI used to emphasize that the system is anti icing and not de icing, i.e. arm it before you entered icing conditions, since the system was designed to prevent ice accretion instead of removing it once you'd picked it up. Of course there's a world of difference between a van and a 125 when it comes to being able to outclimb icing conditions.