Part of the EPQ process is iterating your research question - so you could start with what you have (and ensure you reflect on these iterations)
I supervise Masters dissertations, which in some ways can be similar - finding a good research question is a bit of a spiral:
1. Pick a question
2. see what data and literature is out there
3. Iterate your research Q based on (i) is there enough literature to work with (ii) can you find / generate enough data to work with?
sometimes you go round more than once . . .
Usually, the more precise you can make the research question the easier your literature review and data seeking will be, but its okay to start wide and zoom in