Closing a Bank of China account for a deceased relative who lived abroad?

Hello, my mum lived in the UK and had (we think) a BoC account in Hong Kong. She passed away and I'd like to close this account when I'm visiting Hong Kong in a few months time. I've tried calling the HK office but have not managed to get through to anyone. I spoke to someone over email who just told me they needed the death certificate and some ID from me to show we're related (so birth certificate I guess). They wouldn't tell me if she still had an account with them. While clearing her belongings I found a lot of BoC letters but they were all from years ago. No recent ones so I'm not sure she actually does still have an account.

Does anyone know if that's all the needs to be done to close the account? We don't need to apply for probate. I'm an executor of the will - do I need to bring that as well? I'll only be there a few days so I want to make sure I'm not spending all my time there sorting this out!