Opening a .blend file seems to have changed my layout from the standard one (2.80). Can I:
a) Reset my layout to be the original one that came with Blender (I can’t find anything now)
b) Make it so that opening a .blend file won’t reset my UI, but still open the scene?
When opening a Blend file that someone else has created (or even one created by yourself in an older version like 2.79) untick this box in the file browser. I think it should be unticked by default.
Loading Factory Defaults is useful if you’ve made a mess of your UI setup. Unchecking that box prevents someone else’s UI setup coming in with their Blend file.