Nobody uses polystyrene as suppression, it was almost always used as precision values, or where you wanted low inductance from the extended foil types with the crimped foils, or where you wanted a capacitor that was pretty temperature stable, as stable as COG ceramic at least over the -30 to 70C range at least, but where you needed only to have commercial temperature range. Military range ones were always a lot larger, simply because the film softening point of around 70C meant you had to use thick films to survive 125C operation. 160V ones with 0.01% tolerance and up to around 2uF were available, but were expensive. Smaller values were common though, and tolerance was more due to selection during manufacture to get the close in values, the outliers being sold cheaply.
Suppression are almost always polypropylene, polyester or something with high temperature capacity so as to survive self healing.