Hi, I'm also a mature student (22), and I've applied to LSE and QMUL and a couple others. I have no idea how they choose mature students, or if they have a different way of doing so.
Neither school has made a decision for me yet, but I'll post here as soon as I hear something! LSE did send me an email on Monday saying "This email is to keep you informed on the progress of your application, which is still being assessed at this time." But that's all.