I would have to say no I'm afraid.
I took 2 Pre-U's and two a-levels the first year pre-u was introduced and I found it made absolutely no difference to my medicine application process. They view a D3 as equivalent to an A so in fact it works against you in many ways since its actually worth slightly more in ucas points and a harder exam.
It's worth remembering also you cant retake Pre-U's and they are not modular as a pose to A-level so you have to remember 2 years worth of information for the exams (although with the changes happening to A-levels in the future I am not sure how they will compare).
In general many of my friends also did Pre-U and did not find it benefited them on any course even ones offered by Cambridge/Oxford who write the exams. In my opinion you should stick to A-levels and make life easier for yourself.
Any other questions about it, feel free to PM.