Mine was an absolute problem. Of courrse you work your way around all the bolts to remove then you get to the tricky ones inside the door. I found it easier to take the indicator out then you can reach in fine otherwise its a bit of a stretch from the brake disc side. You need to pull back part of you lower skirt to acces the two lower bolts to wing. All my bolts cam out easy apart form 1 to the door side and 1 under the skirt. I messed about for ages the bolts wasnt budging. Why on earth bmw use those stupid torx stlye bolts its easy to round them off. So out came the angle grinder the wing came off 5 mins later
PVR, hope you are sitting down for this. Finally picked up my skirts and rear bumper from the painters this morning, and with Bing popping round tomorrow (hopefully) I started to strip the car in preperation. So how it started off You were only meant to take the bloody skirts off...
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Easy enough job, but as said you need to remove the side skirt first to get to the bottom two screws. Likewise I removed the indicator to access the two inner screws.
You also need to partially remove the front bumper to get to one of the screws.