Thanks so much, that's so helpful and really reassuring! I'll definitely keep this in mind once I manage to secure a vac scheme and try to stop overthinking for now haha Best of luck with everything!
I agree with that reply, best not to dwell on it too much but you can usually figure it out a little though, and in many cases it is something worth considering (e.g if you have two schemes that clash). For example, my friend has a scheme coming up with a firm soon, and they weren't explicitly told much, from googling she figured out they take on about 25 trainees, they have around 30 vac scheme places a year, and they also open a direct training contract route later in the year. So she's surmising around 20/30 may get an offer.
However, everything is guesswork, and there's a lot of factors involved. E.g in the case of this firm, if all of the vac schemes were absolutely perfect, they might offer a TC to as many of them as they can and just not open the direct TC role that year. If they are all awful, they might not offer any, and would instead take on only direct TCs. What I've heard said from multiple firms graduate recruitment (though this definitely isn't applicable to all firms), is that if you can impress on the scheme, they like you and want you and think you'd be a good trainee, there is typically flexibility to offer you the TC. Whether that's a spot in an earlier cohort (provided you've finished your studies), or offering you a later cohort (i.e three years in advance instead of two), or even making an additional spot in the current cohort, they will work it out.
So I'm taking that and running with it, do the best you can and it will (hopefully) all fall into place.