Renouncing Brit Citizenship: A few questions

Hi all

I'm a dual Brit/Irish citizen. I will be renouncing my British citizenship in the near future so that my non-EEA civil partner can get an EEA FP and travel back to the UK with me. As a result of the renunciation, my current British passport will probably [not sure] be retained by the Home Office and all the Entry/Exit stamps inside will be lost. I had planned to use these stamps as proof of our travels as we have many common stamps [mostly in my British passport] e.g. to Hong Kong, Malaysia, Thailand, Vietnam etc.

Questions:
1) If I make a copy of every page in my passport, do you think that other Embassies (e.g. the Irish Embassy) would accept this as evidence of our entry/exit to these different countries? I know this forum is about the UK, but do you think that the same would work the other way around (e.g. photocopies of entry/exit stamps in another passport used as proof of travel together)? Would they need to be certified?

2) I know it is possible to renounce by just submitting my birth certificate. Do you think that they would return my birth certificate to me again when they return the confirmation of renunciation? There's no way that my birth certificate records can be 'deleted' or destroyed by the General Records Office, right?

Thanks a lot
Best
CC