BMW 320d SE
Tried again to find the leak. Used a watering can. Seals near the lights are fine. Couldn't replicate the leak. It rained and yet again, water in the boot. Following the trail of water, it seems to be coming from in side the rear near side wing above the lights. In my mind, it can only be from either the aerial base or the large rubber boots around the tailgate opening where the wiring and washer tubing enters the bodywork.