I agree with what Euapp has said.
Addressing the gap year, quite a large % of vet students are not straight from A Levels, I'd even wager at least half on my course are not (although Liverpool gives out deferred offers regularly so that probably has an impact). I took one after I got no offers the first time I applied (not uncommon) and while I never wanted one in the first place, it was the biggest blessing in disguise. You don't have to be 'stuck at home', nothing is stopping you from going to visit your friends at different unis throughout the year to get the student experience without the commitment! And you can spend your time however you want - many people travel or engage in hobbies throughout their gap year. I had mine during covid and I'm not a travel fan so I didn't do that, but I did do plenty more work experience including a stables in return for free riding, and I also worked at a restaurant which really helped boost my savings for first year. I grew up massively over this time, being away from education and getting a glimpse into the 'adult world' was really beneficial for me and I look back on it fondly - plus it gave me a year of 'resting the brain' before starting a very intense 5 year degree. Overall 10/10 recommend a gap year. You also have to remember if you are considering a vet course, you have to give up with comparing yourself to what your current friends are doing, for many reasons. You will not be graduating at the same time, so you will be seeing that + them moving on with their life from uni, which can be a little 'ugh' but that's just how it is, so starting a year later than them will not prevent that. You will likely be at different unis anyway so won't see each other as much, especially with placements taking up a godo chunk of your holidays, BUT you will make new friends at uni and you will have similar holiday periods for the first 3 years at least so you will still be able to see them when you are home.
As to struggling with A Levels, I literally struggled through chemistry WAY more than I have ever struggled at uni, so if that is the issue subject I wouldn't worry too much. Although the vast majority of the course is biology-orientated since you are learning about all the different body systems etc, so if you really struggle with biology (particularly the non-plant stuff) it would be more of an issue. Ngl first year of vet med was a giant step up from A Levels, but more in terms of the pure amount of content rather than difficulty in understanding - while some topics obviously will be harder than others, I do feel we basically cover the content of 3 A Levels worth in 1 semester, and obviously you won't get as much support etc as you do in school.
So the work experience issue is more of a red flag, although I will say I'd be totally lying if I said I thoroughly enjoyed every single work experience/EMS placement I've done. I've certainly had ones where I couldn't wait to leave. And yes, as a pre-vet student the clinical work experience is normally a little boring because you are stood there, not really involved, and it is normal to not even know what questions to ask - I was in that position, but now as a third year I do absolutely love most of my clinical placements because I obviously get to be more hands-on and I have meaningful questions to ask because I've had the teaching. So if you think you just don't enjoy particular work experience (e.g. I am very not farmy, and while I try to gain as much as I can from every placement, I can't say I loved all of my farm stuff) or it is just because you are at a pre-vet stage, it might not be as big of an issue as you think. However if that is not the case and you do hate every placement and don't think you'd start enjoying it more as a vet student, I don't think vet med is necessarily the right course for you - as you said, you do have to give up a lot of your free time in order to do these placements, and that is how you actually learn the most. Work experience is there to show you whether you actually like the job or not, so if you really don't enjoy the experience, it might be showing you that you do not.
In terms of work-life balance, it is definitely doable, but it isn't the easiest thing. You do get time off on Wednesday afternoons for sports etc, and you really don't have to spend every evening and weekend doing work. The timetables vary depending on the uni, but many will have gaps throughout the week which if you use to do work in you won't have to do near as much in your free time, but I would think of the uni course as a 9-5 job. Outside of exam seasons where you do want to ramp up your workload with revision, I usually spend 10-20 hours on doing work outside of timetabled sessions (including during the timetable gaps), probably on average 15 but obviously depends on the kind of week we're having, although it did take me a couple of years to actually get into the swing of it so I probably did quite a lot less in first year. It is important to have the time to switch off etc. You can plan so you have breaks in between your EMS placements. I know of people who went out pretty much every night during first year, although I don't know how they did it lmao. I'd say that is a struggle many vet students (and even vets) face, but if you want it enough it is manageable to do.
But overall, if you think that this all sounds awful and you don't want to live like that, it is more than fair enough! I can't say I'd recommend the course to most people, it is really difficult to manage everything and it does take a lot of commitment. It is much better to realise that now than later on when you have already started so have already sacrificed a year of student loan, moving out etc. I can't really comment on what you should do instead, many students look at vet nursing as a backup plan but if you don't enjoy placement etc then you'd probably be doing a lot more of that on a nursing course. Maybe speaking to people such as teachers, tutors, parents etc would give you better ideas.
And if you do end up wanting to go into vet med, I would say you could try and do a last push to get the right predicted grades before October - I would discuss with teachers, subject leads, maybe even headteacher (and if your parents can back you, even better) if they'd be open to you doing additional work between now and end of September so you can 'prove' that you are capable of getting those As, e.g. perhaps offer to do an extra set of mock tests during a free period or lunch etc in your first/second week back. Sure it isn't the most pleasant thing to do over summer, but if you want it enough I'm sure it'd be doable. The worst they can do is say no, although schools generally like their students to go into courses such as vet as it's good for their image, and my school just gave us whatever predicted grades we wanted - it's up to us to meet them in the actual A Levels at the end of the day. Best of luck in whatever you decide!