Ahhhhhhh, I'm so so so sorry this reply is really late - tsr didn't tell me I was quoted, and was looking through this thread just now to see if I could find out where OP ended up and saw this
So I'm going to assume you've applied (or not, as the case may be) by now, but in case someone else reads this in the future, I'll give a few of my thoughts.
Science and maths are some of the most popular subjects at Latymer - according to my geography teacher, there were a grand total of 12 people in my entire year (of 240ish people) who didn't take maths or a science to AS level (and I think he said 2 didn't take maths, science or English to AS? I can't remember, this conversation was a while ago). If we're going by pure statistics (can you tell I do A level maths?
) the chance of a randomly selected Latymer sixth form applicant getting in would be just under 1/5, and the fact that you're going for sciences and maths does put you at a bit of a 'disadvantage' because they're really oversubscribed subjects etc. However, obviously if you have good GCSE predicted grades and are generally doing well at school, your chance is going to increase quite significantly, especially if you're genuinely interested in your subjects (so many aspiring medics are doing science A levels just to get into medicine, not because they have any interest on them), and having extra-curricular stuff would help too (Latymer is very, very big on societies).
But to be honest, there's no point in not applying - it's not like UCAS where you have a set number of choices, and applying to a uni which is a bit of a stretch means you have one less space on your form. So basically if you think you'll enjoy life at Latymer (don't apply for the sake of saying "I go to Latymer", apply because you like the school) you should definitely apply - you've got nothing to lose!
If you have applied, you'll be having your test soon - so first of all, good luck! Remember, the exam is an academic aptitude test, so it doesn't need prior knowledge of anything (everyone who applies, with all their different academic backgrounds and subject interests, sits exactly the same test). It's not like the year 7 test where most people will have done years of tutoring in preparation! There's absolutely no need to stress over it. Oh, and if you find it hard, it doesn't mean you're stupid - the test needs to differentiate between all the applicants, so it needs to separate the 'best' from the 'best' if you like (even though I have issues with using the word 'best' in this case because I think intelligence is very subjective, but that's an argument for another day). But honestly, the feedback I've heard on the test is that it wasn't anywhere near as bad as people expected.
If you haven't applied, I hope you're very happy wherever you end up... well, actually, I hope you're happy regardless of whether or not you've applied
tl;dr sorry this is late, if you want to go to Latymer please apply and don't let the slightly scary-sounding admissions procedure put you off, best of luck! Tell me how you got on!