Help with subwoofer Fabia MK2 VRS

Hello, I am trying to fit a sub and amp into the fabia mk2 vrs. i was wondering if anyone could offer any help of how I could pass the cable from the battery into the cabin as I cant find any grommets that will allow that and was wondering whether the whole dash needs to be removed in order to get the cables into the back of the stereo. I've got an aftermarket stereo so I just need help with wiring it out within the vehicle.

Thanks