Proof of residency for Student finance

Hi. I have done what was required of me for my student finance application but just got an email asking for proof of residency. I am Portuguese and was born and raised here in London, yet on the 5-year residency form, I have to answer questions, such as 'When did you move to the UK' and 'Why did you move to the UK'. How am I supposed to answer that if I was born here?? This is all definitely because I sent my Portuguese passport (don't have a British one, but I am eligible), but the place of birth on my passport clearly states 'United Kingdom'.
I am considering sending an exam certificate for GCSE and AS Level as proof btw.

Thanks