That has happened to me a few times here in Columbus, OH since I order a lot of (non-watch related) stuff from eBay.
Apparently big cities with lots of ZIP codes have one sorting facility are where things arrive and are then sent out to the local post office for delivery. What has happened to my packages when they go from sorting facility to "out for delivery" back to the sorting facility is that they've accidentally sent it to one of the many other (and in this case, wrong) post offices across town.
You would think (hope?) that the wrong post office would just send it to the RIGHT post office for delivery the next day, but instead they send it back to the sorting facility and THEN to the right post office, and then it's delivered shortly thereafter.
Hopefully your package arrives soon, but at least it's made it from the UK to the general area within LA!