If you download one of the many available "real time" bus apps (I use Probus London) you'll be able to know exactly what time the next bus will arrive at the bus stop, allowing you to leave the hotel just before it's due. Tell the app to show you the nearest bus stops and select stop BW. Don't forget to take into account the distance to the nearest pedestrian crossing/crosswalk and how long it will take you to get across the road.