What sort of camera are you using ?
Channel 4 unit is irrelevant as they will have their own sets of acceptability, however I am surprised.
An ND filter may well be overkill.
Bracket to merge or HDR sound like good options; you or a friend will need PShop or similar to take advantage of these.
I tend to use Aperture Priority but that is because of the sort of shots I take. My camera has all sorts of options but should I feel the system will not produce what I wish, then Full Manual is the way to go, of course some understanding of the principles is required.
Or just shoot a load, see how they look and re-shoot with the best set of settings.
My credibility may well be doubted, so some of my stuff is at
https://www.flickr.com/photos/47885101@N07/sets/