I'm ever so sorry but I'm quite sure this can't be done. I had long conversation with my Head of Year and a few of my friends about this, as I wanted to apply to two quite wildly different degree courses (in my case, Geophysics or Mechanical Engineering) I was told, that as UCAS is fully electronic nowadays there is no opportunity to add separate personal statements for individual universities.
Unfortunately for me, and likely many others, it would mean all applications having the same personal statement attached, regardless of what course is. For me, this was causing quite a problem, as for the two courses I would have liked to emphasise different out-of-school pursuits - and most importantly, why I would like to study that particular subject. I can hardly say how great an Engineer I could become when Geophysics admissions tutor is reading the application!
As I was told it wasn't possible to submit separate personal statements, the advice given to me was this:
If you try to write a single personal statement with two courses in mind, it is likely that both admissions tutors will consider you not committed to their course (well, you're not if you're considering another course) and therefore you are unlikely to receive offers for either course.
Thus, quite simply, my Head of Year told me to pick one of the courses. (It has very much simplified my decision-making I now know which course I'm going to apply for - Mechanical Engineering)
Just on the off chance you're applying to Cambridge for Natural Science or Engineering I'm told that there is a section on the CAF to add a little more to the personal statement, which is only seen by Cambridge.
I hope i haven't dissapointed anyone wanting to apply to two very different courses - and i bet there are a lot of them....you really would have expected UCAS to sort out some sort of system for this?