youve probably already done this job, and hopefully without any hitches, but it wanted to add a little something to the advice.
Marking all four holes at the start is a good move, but when drilling into brick/stone it's not unusual for the bit to move off the start point until it gets good bite. I would recommend drilling the first hole, line up the plate again, then mark the next hole. Do this for each one to avoid screws going in at odd angles.