UCAS has given you 47 lines (or 4,000 characters) for a reason - they expect you to use them. If not all of them, then the vast majority. If you cannot do this then you need to go back to the planning stages as clearly you are not going into the detail that will be expected of you.
One of the worst examples of this that I have seen over the last 12 years was a dentistry applicant who felt that a short 5 line statement would be enough to get them into one of the most competitive courses that exists. Thankfully this example is extreme and it was, quite clearly, a lack of understanding on expectations. But there are always students who think that academic standards alone are going to be enough to get you onto the course of your choice. This is simply not true. Even with an A2 prediction of 4 A*s, a 5 line personal statement will never be enough. And nor will 25, or even 35 lines. 45, however, and you’re in with a good chance.
If you are really struggling with the length of your personal statement then don’t panic - get it reviewed by someone who is familiar with the application process (a careers adviser, a tutor) and they should be able to spot areas that you have either missed out completely or that you need to expand upon. As I have said before, it is very rare - certainly in my professional experience - that a statement is deemed ‘perfect’ at first draft so as long as you have completed it in plenty of time, it is a problem that can be quite easily overcome.
Don’t forget that Momentum Careers Advice offer a personal statement review service for just £45. Email firstname.lastname@example.org if interested or read my blog post What is involved in a UCAS personal statement review?
If you want to browse through the other blog posts that I’ve written on the subject of UCAS applications then please click on this link.