Hi OP,
First of all, it looks like you've been really organised with booking your w/exp in, and that looks like a great selection of places.
Just remember that it's not necessarily quantity, but rather quality - what I mean by that is you could have one school student spend every single day of their entire summer holidays on placements/ work experience, but it doesn't mean that they make the most of the learning experience. It's WHAT you do whilst there (ie. How you conduct yourself, conversations and interesting interactions with vets/farmers/clients if opportunity arises, constantly linking back what you're observing and learning on placement to the theory you're being taught in science lessons etc, learning to think in your head "what would I have done in that situation?"). As someone who is very susceptible to comparing myself with others, and viewing myself negatively, it is so easy to fall into the trap of becoming competitive to a self-negating degree. Don't let the whole hype on 'vet students-to-be need so so much w/exp and the more the better!' get to you. It's what you do with your w/exp that counts, not just how much you've got.
Okay... So...
I'm halfway through my vet degree, but have been off due to medical reasons for last 13 months
Anyway, I just wanted to say that the vet course is, in my opinion, not so much about "wow it's so hard" or "it's so academic", I've found that these are stereotypical/generic assumptions. Yes, agreed it is not easy - but every course is hard in its own ways- and strong science foundations and work experience prior to applying are both useful. The fact you are already aware of the negative comments people say about grades and time deadlines with the vet courses hopefully means you are also aware that a lot of the stuff being said about it is myth!!
This is just be humble opinion, and it's going to sound a bit cheesy, but I think if you have that passion and drive, genuinely in your heart that you want this vocational qualification, and you are happy to make it a way of life, then that's what the universities are looking for. I spent a lot of time listening and watching others during first year of uni - I'd gone all out with the work experience, ending up with over 30 weeks by the time September start of semester came around - and realised that every single other student in my year had come into the vet course with completely different scenerios. Some had only gained 4 or 5wks w/e, some had never been near a horse in their life, or had only been around horses and never worked on a darn before; whilst others had taken several gap years and worked at pdsa hospitals or similar. Some had received lower grades than expected, but were still there.
Therefore, after much reassessing what I'd been told for so many years (similar things as you, about "you have to start early" and "you can't have a life AND become a vet" - shocking, but true things I was told by careers advisors etc), I came to a realisation : there is obviously no magic "secret" to becoming a vet student, and then eventually a vet. It takes hard work and dedication. But I think the interviewing panels at whatever universities you put down are all going to want to see the core elements of your personality - approachability, professionalism (or as close as can get at age 18, if you apply straight from school), hard worker, proactive, independent thinker (this is a big one, they are always asking WHY and HOW because so much of becoming/being a good clinician is to be constantly analysing and questioning and considering), and able to find a balance.
So I think that, as hard as it is, only you can truly decide if you feel ready to apply this year. You are obviously aware of the demands of the application process, with the longer interview period etc. You're still only yr 12,and whilst your forward thinking is great, just remember that if you feel rushed or need a bit of a break at any point next year, don't be afraid to listen to yourself. I wish someone had told me when I was at your stage to take some time out from the "vet-applicant bubble", and also to realise that the vet schools don't want perfection. They look for people who are balanced and seem as though they are going to cope with the course - academically AND physically/mentally.
Just a last bit of advice: Whatever happens, I know it doesn't always seem this way at the moment, but if something 'doesn't go to plan' on your journey to applying to vet school, then don't panic or be hard on yourself. These things generally work out in the end, somehow.
And the vet schools do talk to eachother. If you end up being turned down by one, two or maybe even three of your four choices, but have an interview at the fourth, it's because the teaching styles vary at each university, and they think you'll be happiest and do best at a different uni. They all end up sending good vets into the world, so keep an open mind to the different universities and don't get too preoccupied/don't set your heart on just one. I got straight out rejections from two of my four choices, on the very first day after the applications went out. I thought that was it for me. Three months later, right at the end of December of yr13, I got two interview invites on the same day from my other two. Then I didn't hear back about their decision until the middle of April, and having given up hope, got both offers. Some people got four interviews and four offers, some people got one offer. That's all you need
I really wish you the best of luck 🍀🙂 and have fun with placements.
EDIT : your w/exp requirements for universities are obviously going to be different for your year due to the pandemic! I imagine some guidelines have been published on the vet school websites. I know for vet students, EMS requirements and the whole RCVS course content and structure has had to be changed completely. So it's going to be worth having a check on that - I'm afraid I only know the new placement rules for students, I don't know about applicant requirements this yr.