Thank you all so much!
So the head said that admissions tutors are increasingly getting tired of seeing the same identical applicants i.e. Econ, Maths, FM, Physics or Chemistry or etc and that, across the board, they'd like to see more of a breadth (as much as you can with only 3-4 subjects). They also said that History, which I know, is a very rigorous subject and that showing strength in Maths/STEM AND a rigorous humanities subject looks impressive and would be useful too.
@pimplebum they don't do Econ at GCSE but do it for A-level (think this is not uncommon). Saturday jobs and extracurricular - as opposed to supracurricular - activities are not taken into account for Oxbridge. Yes YP = Young Person.
@Dearover That is interesting re your YP's subject mix. Yes, we've seen the requirements online - e.g. History not Econ - but just assumed that most applicants would have at least ONE of the subjects for PPE (i.e. Politics, Philosophy or Econ), and it certainly looks that way when looking at freedom of information data. That is encouraging then. YP can't take part in outreach programmes as they're at an independent (a highly selective one so they will need to have near all 9s at GCSE) so will just have to have that slightly stronger application in order to compete.
@NetballHoop was this for PPE? We were thinking of asking but slightly worried as YP has not yet set their mind on whether they'll go for Econ & Management or Econ OR PPE (this is at Oxbridge, they will apply to other unis too of course). They may even apply for a STEM subject so it looks perhaps a bit diluted if asking questions like that? Wish there was a way of asking anonymously!
@poetryandwine as always, thank you so much for your detailed and helpful reply. Yes, we had seen via freedom of information data that the successful Econ candidates at Cambridge had a very similar profile in terms of subjects. Realise that ultimately, the entry test such as TMUA (Cambs) or TARA (Econ & PPE Oxford) will be key too. Hadn't thought about the impact of most incoming students having Econ and so tutors might skim through the introductory courses which would potentially disadvantage someone without it at A-level - good point, will check on TSR. I agree that YP needs to decide at some point. They love maths, sciences but also loves reading the paper, following the news, history and is interested in most things which makes it very difficult!
@MarchingFrogs Yes, I think it's MOOCs and lectures etc that they will need to focus on. I think the 4 subjects they're considering is too much for then also doing an EPQ.
Saying that, even though they are (and this is not a boast) a really strong allrounder who does well in tests, they are also a dep and mature thinker and with a real 'sparky' mind, they may not even want to apply to Oxbridge.
Would be a shame as they would totally suit the teaching set up there with tutorials etc. They are super engaged in lessons and often 'thinks out of the box' and asks interesting questions (according to teachers).
Thanks again for all the advice.