Hi Neil,
Bumps aren’t necessary on the UDN. Issues remain open and in-queue until answered, although sometimes it can take a little while to get to it, or until the proper individual becomes available or the information is gathered. However, all questions get addressed.
The ability to lock files when Checked Out is an option that you will need to enable in Perforce. This is not handled within the editor, but once you do this it should resolve many of the workflow problems you are facing.
Ultimately for this question, we recommend not working on just one single giant level. The best practice in this case is via Level Streaming. Although the documentation is not yet up-to-date, the principles still apply. Your main level is the Persistent level which could potentially be completely empty. Into this you load all of your sub-levels. Not only can you use level streaming to load and hide different areas of the map, but you can even include all of your lighting in one sub-level, and all blocking volumes or sound cues in another, etc.
The preferred method for handling the Streaming is via Level Blueprints, although traditional Streaming Volumes are still available. Don’t forget to search the UDN as a source of information in lieu of documentation:
https://rocket.unrealengine.com/questions/6595/how-to-stream-a-level.html
You also have access to the World Browser, although this tool is still a work in progress and currently has no available documentation. This tool allows you to edit large worlds made up of streaming levels by adjusting their position and streaming properties. The World Browser can be enabled in the preferences under ‘Epic Labs’ and then accessed via Widow > World Browser.
Hopefully this has helped to provide a brief overview of your options. Feel free to reach out to us as you have questions or come upon specific issues.
Cheers!