wiring into engine compartment

I'm trying to add the missing outside temperature indication to my converted NV200. I need to take the sensor wiring from the driver area to the engine bay. There is a rubber bush that has wiring from the throttle and break pedals going through and also a white/brown single wire, that looks like it was added as an afterthought possibly by the converter (Lunar), close to where the steering knuckle is just above the foot pedals. Is it ok to push another wire through this bush? If it is then the remote sensor can run round to the front grill without problem. As the sensor is attached to the display unit the hole would have to be about 6mm but then could shrink back after the sensor was through ( the wire is only about 1mm) Otherwise any other suggestions as to route. I did think about a wireless remote sensor to avoid the problem but siting the sensor is harder as it has its own battery and is thus much bigger to get in behind the front grill.

Thanks,
Martin