To offer another parallel line of approach to the above, if the template they are giving you to follow is in Word or OpenOffice format, than I would say that in most cases the easiest and best way to use it will be to go through all of the styles that it needs to format the text properly, and then create those styles in your project. Don’t worry so much about what they look like. That can be whatever you want in fact, and I encourage using formatting that suits your eye rather than by rote, labouring to make it look as someone else wants. The key thing here is the styled text is compiled as styled, and such text can be imported or inserted into .docx or .odt file such that the original formatting is stripped clean and the whole thing adopts the desired template design automatically.
I know less (okay, almost nothing) about this in Word, but have done quite a lot of testing and application of the theory in LibreOffice, and share some of my thoughts in this post, which itself links off to a few more practical examples of the workflow (including sample projects), as the post itself is more an abstract overview, and expansion on the above summary.
Otherwise, I myself would go the Markdown route, via Pandoc or Quarto. The above workflow is compatible with it in fact, and if anything requires less overhead because the quality of the .docx/.odt output is a lot cleaner and more friendly to a stylesheet driven way of working, than Scrivener is out of the box. That other advantages to do so are in any kind of content that goes beyond paragraphs of text. Figures, equations, tables—all of that will just be better using Scrivener’s markup workflow.
And yeah, if Open University takes .tex files, that LaTeX project template will get you well on the way to integrating with any boilerplate they provide.