Ok, so I got around to making this in python a few months ago, but I forgot to post this, so I might as well post it now. All you need to go is to open the overworld file in some Hex editor (preferably HxD) then copy and paste the entire thing into this, and it will basically present a lot of data neatly.
I didn't use it as much as I thought I would but hey, it works.
Overworld data parser.exe