Should I say why I am leaving my current university in my UCAS personal statement?

I am applying to start at a different university next year,. I have written about the good grades I have achieved in my assignments, but should I mention in my personal statement why I am leaving the university?

Be honest, but not so much so. Try not to bash your current uni. Something along the lines of, 'I believe I would benefit more at X university, as my current university...' Not as cliché, but you get the drift. Good luck!

I am applying to 5 universities though, so not sure how to word it

So, something like...

"I feel as though I am not reaching my potential at university X. Therefore, I have ensured that the universities I apply for this time around are best suited for my needs, and will allow me to succeed."

Once again, this but less cliché.

I'm at uni now and have just applied to study at a different uni for 2016! i didn't mention already being at uni at all in my personal statement and have already received an offer from the uni i want to go to instead

Not sure, I presume they'd have access to that information as I have already applied to UCAS once before and my college wrote my reference both times.
Do you want to do the same course at a different uni or a different course?