Hi sorry to high lack your post but I have the same issue, I have found the black and yellow cable in the light switch plug but there are 2, does it make a difference which one I use. many thanksyou can get a feed from your light switch. as you open the drivers door there is a side panel on the dash, take this off and there you can see the rear of the light swith. there will be a black and yellow cable you can take a fed from this.
hop this helps