Not being a drone cop, just FYI for your planning.
You stated flying over populated area, you did not state how dense or populated. Small town should not be a problem.
You should not need to go up to 400' unless your trying to get a wide shot of the whole town. Otherwise everything will look smaller than needed and require more zooming in post.
Look for your highest objects, usually the town water tower. Put your altitude maybe 25-50' higher than that. Also set your RTH altitude to this height so if you have a RTH situation you will clear the highest objects on the way back. Once you get your shots around the tower, you can go lower for any unique shots. Have someone with you to watch for hazards. In a small town, power lines, phone lines, and trees are the most common items causing an accident as they are hard to see. So unless you are very close and can see them try to stay above the height of the utility poles/trees.
Flying DIRECTLY OVER PEOPLE and OVER MOVING TRAFFIC is a NO NO. Directly is the key word. With the altitude your planning you can be just a couple of feet off and the video will still appear to be over the subject(s)/traffic, while not actually being over them.
The AIR is WIFI not OccuSync, so be aware of cell/radio towers or other possible interference.
DO NOT FLY AROUND A BUILDING OR OBJECT where you lose Visual Line of Site (VLOS), or you will lose your connection, and most likely lose your UAV.
Be aware of wind direction and a safe landing zones, so if you do encounter problems you have a safe zone to fly towards. Flying direction is important so if you are flying forward your UAV will continue that direction should you lose control. Wind direction is important because say you are hovering near a crowded area and the wind is blowing towards the crowd, that is the direction your UAV will continue or topple towards should you lose control.
Its all about planning and safety. Fly Safe and I Hope your video turns out great. Please share when done!
SORRY RonanCork, I just looked at your profile and saw you were in Ireland. So I am not familiar with your rules regarding flying over people and moving traffic. It is still a smart practice, but you will have to make those decisions based on your local guidelines. Still looking forward to seeing your video.