Eu- non eu separation. Inform Home Office???

Hi. I am non-EU national and my wife is EU. We are living separate for about 5 month now, but not filling divorce yet.
Ive got 7 month till i can apply for Perm REs. So i want to get it first and then divorce.


Few questions:
should me or my wife inform UKBA or home office about separation?
If yes and we didnt - what then?
How long does it take to abtain PR and would it be possible to divorce in time when my documents were porcessed by HO for PR?

Thank you very much