If you're at the stage where you can place your notice then the difference between a PVR and 'Notice' is largely immaterial. In fact it may be better to put in an 18 month PVR over the Notice: with the Notice you are given a completion date and that's that, should your resettlement not go to plan or some other unforeseen glitch happen you are stuck with that date and can do nothing about it. If you need to change the date you have to cancel your Notice and then re-submit it again - there's no flexibilty. Whereas with a PVR you can simply apply to bring the outdate closer or extend it if necessary..... they can't block your notice though. It just takes 6 months longer in most trades than a PVR does but I believe it is much easier to plan your life around.
BTW I'm not the expert, I'm just quoting what my HR Admin people advised me to do when I left (yup, I PVR'd rather than Notice).