Hi
@Deggs_14,
Good question - and I know (and remember) the personal statement can be a real cause of stress during the application process.
On this one, I can only really speak for us, but the answer should cover many universities. In short, a personal statement (excluding any cases where it includes something outlandish such as foul language or abusive content) will not see an application immediately rejected.
To go into it in a bit more detail a personal statement typically serves two purposes: to help us come to a final decision on any borderline applications, and to help more mature applicants take up places on courses when they don't have the academic qualifications but do have relevant experience that makes them suitable. For international students, there is a bit more importance to this in terms of being able to come to the UK to study, but I won't go into that.
A good personal statement is absolutely worth your time, and as you apply for courses with higher competition (at universities with the very highest tariffs and for professional courses such as Medicine) it can make the difference. That being said, at the same time it is part of your wider application, and a couple of lines aren't going to see you immediately written off.
We do have some personal statement advice available for many of our courses. I like to show people
this page for Computer Science. If you take this advice and apply it to your course of interest I think it holds up exceptionally well. To answer the last part of your question, the two things people are never a fan of are irrelevance and a lack of care in proof-reading, so make sure you keep it focused and get somebody else to read over it in case of errors.
I hope that helps! I'm happy to take any followup questions you may have.
Jamie