Not sure where you are based, but if is in the UK, it is also possible to qualify for the double-tier points on BA holidays while flying on Qatar planes. You need to book via the BA holidays website, and you must meet the requirements - for UK based that's either 5-nights car-hire or 5-nights hotel on the same booking. Other key thing is that you must choose flights with a BA flight number.

BA website sometimes doesn't give you absolutely all the flight choices available on the Qatar website, but usually you see most of them.