Dear switchlanes......
It's a really dicey matter. You definitely can't get a reissue passport before six months to your expiration. That begins from May 2014. But also remember that your visa validity is one year after your medicals or the EARLIEST passport expiry date of the principal applicant, spouse or dependants passport, which ever date is earliest.
When did you do your medicals? You should plan to land within one year of that. If your passport expiry date is after your medicals date, you have absolutely nothing to worry about if you plan to land before your medical expires.....(you don't have choice about that, anyway.....) But if your passport expiry date is before your medical expiry date, then, you might need a reissue passport if the PPR doesn't arrive before May 2014.
All in all, your passport is renewable, your medicals isn't. So, the plan still remains to land before medical expires.