This might sound like a stupid question, but will I need to bring my own copy of the thesis to my viva? (I'm in the humanities, so my thesis does not contain any equations or formulas that I'll need to refer to).

Yes, that would be helpful. Considering that they might ask you: "...on page 23 you said..."

Most definitely! After all it's an 'open book exam'. You can also take articles/publications, or anything else you want in.

It's also helpful to put sticky notes, and highlights in the thesis.

Had my viva yesterday and would definitely say take your thesis in. My supervisor advised that I remove any post-it notes from it first though. I also took in copies of additional data.