GANTT chart MAY be useful, or you could just do it simply like I did. By the way you are kind of late with starting the project, people in my new school started it in like March (many have quit or still not up to speed), I started in September and now I am milesss ahead almost done with like 70% of my essay.
Basically I would recommend first making a plan of what you want to get out of your project, outline where you could go with the project potentially and then choose the "route" you like best and stick with it like what kind of research you want to get done, primary research, etc. In terms of planning you could simply just write down the deadlines you want to set yourself with specific dates, and say how achievable these are and what might affect them (I've been told it means I will be able to reflect on them better). My EPQ coordinator told us to use GANT charts but I haven't because there's no need for it. It's your project. Do what you feel best and what suits you.
Good luck, and try to get as much done in half term as possible because the final submission isn't even that far! Ours will be in December, not sure if it's same for everyone but yeah not that long to go.