At many COE weddings, the vicar walks in front of the bride and her father, almost completely blocking the view of her, with her following bridesmaids. Most civil ceremonies I've done, it's been done both ways, the registrars aren't bothered. If you are marrying in a church, the officiant will tell you how they do it. I had an American bride a few years ago, who insisted on doing it the way she'd always dreamed of, and the vicar wasn't very happy about it.
Being American, I will stick up a bit for the American way, because it does showcase the bride more. The bridesmaids do enter first, one at a time, one after the other, but each waits until the one before reaches the front, and they stand to the left side in support of the bride, and mirroring the groomsmen on the opposite side. Then if there are flowergirls, this is when they enter. Once all bridemaids have entered, usually the music either changes for the Bride, or it gets louder, and that's when everyone stands. Up til the bride enters, everyone is sitting.