These are the small 0.01uF or smaller capacitors with transparent edges and you can see foil in the innards? If so, I think you are talking about "polystyrene capacitors". Yes, they were extremely popular in UK/EU for at-chip decoupling capacitors in the 1970's and 80's. They are not polarized. I'm not sure why polystyrenes were so popular for bypass/decoupling in EU and not so popular on this side of the pond. Here in the US we were more likely to see polystyrene in audio filtering/coupling locations where the cheapest ceramics had odd piezo properties and low leakage of polystyrenes were desirable. I do remember seeing polystyrene bypass capacitors on at least a few DEC boards of the 70's so they did make some inroads. There are real glass capacitors used where zero leakage and zero soakage are uber-concerns.