Finally booked via AmEx Travel in the UK paying in GBP. Ticket issued but there is no way to Manage my Booking or complete online check-in for any bookings other than those made directly through Air China's website...
Is this airline stuck in 1995?
if you need to speak with Air China again, this page (provided by another user in another CA thread) has some London phone numbers that worked for me.
https://www.airchina.nz/NZ/GB/contact-us/european/