any advice for y13 and applying for uni?

just looking for advice for the start of the new academic year i'm applying for e&m at oxford, efds at imperial, econ at lse, ucl and warwick. i'm doing maths, further maths, econ and cs - all exam boards are edexcel apart from cs which is ocr. i'm on the analysis stage of my cs nea right now. anyway, if anyone has any advice in terms of these a level subjects or uni applications i would be very grateful!!

I did Edexcel maths and FM, so I can advise there.
Both subjects require regular practice to excel in. This can be done using past papers, marking them (asking for your teacher’s opinions if in any doubt) and keeping a record of questions you have lost marks on (and why).
You may find it beneficial to explain how to solve past paper questions to less confident classmates, especially for when you are prepping for interviews.
In terms of resources, PMT is the best by miles. Examsolutions, mathsgenie, Bicen maths, the AMSP and Tayyub Majeed are also excellent. Pick your preferred resources from this bunch and use them exclusively. You may also wish to use integral maths and Dr Frost if you have access to either, but I personally never used integral maths (and so can’t vouch for it) and found DFM rather useless.
Whilst I know nothing of E&M specifically, I am an Oxford student (studying chemistry at St John’s college) and have some useful insight for preparing for uni admissions.
I assume by this point most of the important detail on UCAS is sorted and the rest of my advice will be Oxford-centric.
First of all, for Oxford, pick a college. There is a college suggester that you can find here that accounts for your course and other preferences and needs you have:
https://apply.oxfordsu.org/colleges/suggester/
My advice would be to consider attending an open day if you haven’t already and looking round a select few colleges from the list.
You will need to sit section 1 of the TSA, which will mean finding past papers, attempting them and marking them. It should be the same procedure as with using past papers to revise for GCSE and A level.
https://www.ox.ac.uk/admissions/undergraduate/applying-to-oxford/guide/admissions-tests/tsa
Whether you get as far as the interview stage or not, it would still be advised to prepare for an academic interview regardless and as soon as is possible. Success in Oxford interviews hinges on your ability to verbalise your thought processes and so this is one of the reasons I have recommended walking less confident classmates through past papers.
You need not wear anything fancy to your interviews - wear something comfortable, make sure you have good posture and are familiar with the technology requirements for them and have them sorted with your school in advance (Oxford usually notifies you of the timings by email a week or so in advance of your interviews)
https://www.ox.ac.uk/admissions/undergraduate/applying-to-oxford/guide/interviews
If for whatever reason you think you’ve misheard anything in the interview, or haven’t heard it at all, do not hesitate to ask if it can be repeated or clarified. The interviewers know the experience is stressful and (most) will be understanding.
I would also imagine keeping up-to-date on relevant news may be an idea as it may form part of the discussion you have in your interview.

Thank you so much for your advice! What are your views on making an open application to Oxford as that is what my Oxbridge mentor at school is recommending to me? Are there any advantages or drawbacks?

I made an open application on my first attempt at getting into Oxford and was assigned St Hugh’s college, which since getting in on my second attempt I have seen and realised wouldn’t have been a good fit for me. I would personally use the college suggester and apply directly to a college that matches your preferences.
Open applications mean you will be assigned a relatively undersubscribed college, so getting in *may* be a little easier, but direct applications will mean that if you are good enough to interview but your college is oversubscribed, you will be reallocated elsewhere (circa 25% of applications end up being reallocated iirc).
You do also have to wonder why certain colleges are undersubscribed. Sometimes it’s the location (i.e distant from faculty buildings you’ll need to access, accommodation being by a noisy main road etc), sometimes it’s that the college is newer and just hasn’t built up as much of a reputation as other colleges and so is basically unheard of. There may be several reasons why - some more important to consider than others.
You also have to remember that different colleges have different policies and so you may be assigned a college that doesn’t offer you accommodation throughout the whole degree etc etc.
I think on the whole, there are more potential drawbacks than potential benefits to making an open application and so I wouldn’t recommend doing so.

just looking for advice for the start of the new academic year i'm applying for e&m at oxford, efds at imperial, econ at lse, ucl and warwick. i'm doing maths, further maths, econ and cs - all exam boards are edexcel apart from cs which is ocr. i'm on the analysis stage of my cs nea right now. anyway, if anyone has any advice in terms of these a level subjects or uni applications i would be very grateful!!

Performing well in the TSA test and ultimately the interviews will be the determining factors for an offer.

just looking for advice for the start of the new academic year i'm applying for e&m at oxford, efds at imperial, econ at lse, ucl and warwick. i'm doing maths, further maths, econ and cs - all exam boards are edexcel apart from cs which is ocr. i'm on the analysis stage of my cs nea right now. anyway, if anyone has any advice in terms of these a level subjects or uni applications i would be very grateful!!

Looks like you're applying to 5 of roughly the 8 best in the country, which is really impressive! However, I would advise looking at one or two universities which could act as insurance choices. Applying to 5 with such high requirements is risky, and I know, having just finished Year 13, that not everyone gets what they expect unfortunately. Hopefully that wouldn't be the case for you, but if something were to go wrong, you might find yourself without a secured place.
Also, since they all have such similar requirements, there's not much benefit to applying to all of them, as they should have similar chances of giving you an offer, and you'll have to narrow down the choice to two anyway. I'd argue it's better to give yourself options with a wider range of offers, rather than 5 in such a narrow band of grade requirements.
Ultimately it's your decision, but for example there's plenty of quality Russell Group Unis with lower grade requirements, and it might be useful to have just one backup in case.
Best of luck with Y13!

Do you think you have time to turn your grades around from like Cs to A/A* ?

I don’t believe the OP has said anywhere that those are the sorts of grades they are achieving.
I suspect you may have interpreted “cs” to mean their grades, when it’s just a shorthand for computer science.

Sorry I mean't that do you think there is time in year 13 to go from C grade to A/A* ?

I totally agree! The choice I've made is based on the pressure from my parents to be honest. They just want me to apply to the top ranked unis and I know there are other unis out there but my parents are just saying I can apply in a gap year to unis with lower entry requirements if I don't get any offers/don't meet my offers this year. I really appreciate your advice though, thank you!

Please try to resist parental pressure (not always easy to do, I realise). You must do what is best for you. Sometimes parents give good advice, but sometimes they don't, and in this instance the advice to apply to five super-competitive universities and not include a fall-back choice is arguably not good advice. Teachers may give better advice than parents on these things.
By the way, gap years are great, but there is also clearing if you were to miss all five of your targets (which of course I hope you won't).

I know but my parents tell me off whenever I bring up the topic so I've just given up. I tried bringing it up to them again last night and they shut it down immediately. Also, I will definitely think about clearing in case I were to miss all my targets! Thank you