Renewing of Z visa & residence permit outside of China

I am living in working in Beijing and my Work Z is up for renewal in May. Unfortunately I will be on maternity leave at that point in the UK (from March to August). Is there still a way to just renew my visa and residence permit or will I have to apply for a whole new one?

Also, if your passport is up for renewal, what would happen? Another issue that I have is that although my passport doesn't run out until 2018, I only have one page left in it which I think means I will soon have to apply for a new one. Would this also require me having to apply for a whole new visa?