I've never noticed much additional noise from a helmet. Either way, with ears, the noise of a headwind feels worse than the headwind itself. The wet only adds road noise to the equation in my experience. I don't like wearing earplugs on the road because I rely on my ears too much for a sense of where vehicles are around me.
Cup your hands around your ears and peddle with no hands lol, i do it on the c2c paths if its that bad. Im sure you can get clip ons for helmets to stop it but youll look daft its just one of those things youve got to live with