To brother HKG3,
Thank you so much for your insights!
Since it's too long to quote I'll just start a new chain of replies
1 - Good for you. Make sure you get an extra certify copy of your marriage certificate from the Hong Kong Immigration Department.
2 - re photos - need to send some photos of you two together for her visa application. You don't need a lot of photos, but enough to cover the time line from the start of the relationship to the wedding and post wedding stage.
3 - should be fine.
4 - My view is that it would be better for she can learn how o drive in her own native language first. You can get her to do lessons on the basics in Hong Kong before coming over to the UK.
5 - Keep her bank account in Hong Kong. It is not that easy for someone to open a bank account in Hong Kong now. If her Hang Seng bank account is only a HK$ passbook account, she may want to open a foreign currency bank account with Hang Seng bank as well (this would enable her to deposit GBP £). She may want to open an UK bank account in Hong Kong before she leaves, but it is up to her.
Thank you so much for your advice

She does have the foreign currency account with her Hang Seng Bank account. Would there be any difficulty for her to open an UK account after arrival? Like do they require proof of residence?
About driving... I talked to her about this and she seems to think it's too expensive to learn how to drive in HK now (around HKD12k I think). So I guess I'll just tell her the basics in Cantonese and let my relative teach her the rest, perhaps hire an instructor in the UK when needed.