Not sure what to do now

I was under assurance from my teachers that my predicted grades would be ABB for a level, so I picked the unis I wanted to go to based on that, so all the unis I've picked want ABB or BBB but now my predicted grades have been sent to ucas by my teachers and I've ended up being predicted a BBC. So now I'm unsure what to do as I can't find a uni that will accept less than 300 ucas points for the course I want to do (psychology)

is it worth applying to them anyway and hoping my personal statement makes them consider me or should I hold off applying till next year?

If your predicted grades have been sent off to UCAS, why are you asking "is it worth applying to them anyway" given that you've already applied? I don't understand how such a colossal misunderstanding could have happened but now that you've applied, you might as well make the most of it, unless you want to change your uni choices (which you can do within 7 days of sending the application off) to more realistic choices. Generally, it would be advisable in your situation to apply to 1-2 BBB+ universities, 2-3 BBC universities and maybe a BCC university.

Sorry, I misworded it, I meant that the grades my teachers will send to ucas when I'm ready to apply have been put on my schools system.

I've been told by my form tutor not to bother applying to any uni that I don't meet the required grades for as my course will be oversubscribed so with my predicted grades they'll not bother looking at my personal statement and just automatically reject my offer :/

You definitely shouldn't apply to many universities with grade requirements above your predicted because he's right, you probably will be rejected. However, great things do happen and you never know - the only certainty is that you won't get in if you don't apply. There's nothing wrong with one ambitious choice if the other four are more realistic.

The thing is, I haven't been to any open days for unis that have their required grades as my predicted ones as I didn't believe I needed to, so if I do apply it means me applying to unis that I haven't even looked around and there aren't many open days left now either