Eton College Orwell Award

I applied about six years ago and didn't get in (in retrospect, thank God), so my memory is rather hazy, but I was shortlisted and spent three days in Eton. I remember applying for Maths/Further Maths, Physics and Latin.
Hopefully someone who applied more recently can correct me if I'm wrong about any of this.
I believe maths is assessed in two ways: as part of an interview, like your other subjects, and as part of the electronic aptitude assessment. I recall there being three parts to the electronic aptitude assessment: a mathematics test, a reading comprehension test and a logic assessment (read: IQ test). You take these in a computer room with the other candidates (I believe this includes fee-paying candidates in addition to Orwell award candidates but I'm not certain), while the subject interviews are one-on-one. I don't recall these being particularly hard? The closest comparison I can think of is the MAT, but that requires the first year of A-level Maths/Further Maths so it might not be the best thing to practice off.
My memories of the maths and physics one-on-one interviews aren't very clear, but I believe that they focus on two main things: your ability to solve novel problems using principles you already know from GCSE, and how much you've studied yourself in the subject. You mentioned trigonometry. You do need to know SOH-CAH-TOA and the sine/cosine laws, but with what I remember I probably wouldn't suggest grinding out circle theorems. Spending some time on maths and physics YouTube may be sufficient to make you look better to the interviewer if you solve the problems correctly.
You're probably not applying for Latin, but if you are then this is the interview I remember the most clearly. You start with grammatical problems and definitions: what's this word? What case, declension and number is this noun in? What tense is this verb in? These problems are non-trivial: I remember receiving both defective and deponent verbs, but if you don't know what these are the point isn't to catch you off guard but see how quickly you acclimatise to the new concept. This really goes for all of the subject interviews: don't get demoralised, smile and try to figure out what's going on quickly. You can ask for hints but don't ask for too many. Eventually, you'll be walked through translating an entire passage. I managed to do "especially well" on this with just twelve or fifteen chapters of Wheelock's Latin.
After the subject interviews and electronic aptitude test comes a pair of interviews designed to see if you're a good social fit. I think one is with the Head of Admissions and one is with the Vice Principal? Really do not remember. The thing that stuck with me the most is that they want to see how morally resilient you are. How well do you respond to failure? How well will you survive without your family, if you fail to break in socially? I successfully got into a co-ed day school that asked similar questions, so my answers couldn't have been bad. Nevertheless, it turned out I was really bad at socialising and had very little moral resilience, even if I wasn't a drop-out risk. It would have been considerably worse for me in a single-sex school. Having failed I would say think about what makes you good at overcoming adversity and what makes you good at connecting to other people and contributing to an environment, and sell yourself to them using that.
They ask you to ask them a question at the end of the second general interview. Don't make it "wouldn't Orwell have opposed private schools," the answer will be "well what we're doing is just, and I think he would have liked to know that we were helping the British working class gain social mobility." It might feel really good but you would have missed a further opportunity to sell yourself and may have disadvantaged your character in their eyes.
I suspect that if you're from London, the grade average of your school will be high enough compared to the other candidates to disadvantage you even if you're from an area in London that's relatively deprived.
Finally, and I don't think this will influence your chances, they let you go to Eton classes and visit Eton societies, so do take advantage of the opportunity. The food is really lush.

Cheers. In terms of maths for the computerised test - I do edexcel - how similar is to a GCSE paper because also we won’t have finished the GCSE curriculum so what in particular should I revise for? And also you mentioned the interviews - do they give you written questions to answer and see how you work or do they go through it with you?etc Thx so much for the info

I don't recall it being very similar to a GCSE paper at all. I think the computerised test is pretty easy and if you just keep up to date with your studies it should be a breeze, but given I didn't actually get in, who knows? Subject interviews have some written questions: the passage in a language interview will be written down, for example, but I think most of the question is explained to you verbally.