Super Resin Polish by Autoglym is very very good, it will not cut away at the finish like some polishes, and leaves a great smooth, polished finish and will remove any water marks ect without cutting, also simple to apply and buff off.
I personaly wouldnt use anything harsh on those pillars or anything that needs too much elbow grease to buff off, once you get a scratch or scuff on that chrome finish it may be hard to remove without causing more damage.
Super Resin Polish is ideal. You can get it in Halfords.
Put some wax on top of it for extra protection, any one of the ones that RCZ1 recommends will do.
I use DoDo Light Fantastic, (recommended by RZC1) it gives great protection, water beads very good and like the Super Resin Polish it is easy to apply and buff off.
You can use both the polish and the wax all over the car, not just the chrome arches and your done for months. :thumbup: