I tried 30mins ago without needing to refresh and managed to book for a slot at Sham Shui Po - initially offered 22nd March, but could select other dates so got for something further out - the appointment times only for after 5pm but I'm so relieved! (might take a while so bring some snacks or eat just before!)
Thanks for everyone's help. If you still can't book online please keep trying at random times as people have said, and avoid doing it at Midnight - as it seems to be time when everyone is trying to get a slot 3 weeks in advance.
So I've finally managed to book an appointment, now they have extended booking allocation to 96 days.
When pre-filling the form after booking the appointment, do I say I claimed British citizenship?
My current HKID says Permanent and I have the Right to Abode, however I am a British citizen by birth - so I'm really confused about how to complete this section.
But then if I do claim that, this may mean I will lose the Permanent status on the card???