Richard Bell with codeshare flights it is the marketing carrier whose baggage rules apply whereas for most other bookings it is the operating carrier. This is a specific exception to the IATA rules.

Too some extent you can choose the currency you will pay for tickets in right from the start of the booking process.
If you look top right on the webpage there is a flag, country and language shown. Select a country that has the currency you wish to pay in. Then everything is in that currency. This may not be true for all countries but it appears to work for most.
For example you want LHR-DOH-SYD return and want to see prices and pay in HKD click on the current nationality and change it to Hong Kong. Then everything is in HKD!
It has worked for me several times so do try it and see if it also works for you.