Others may correct me, but you'd earn enough Qantas status credits (SCs) for entry elite status with QFF (Oneworld Ruby - the lowest elite tier) - which IMO doesn't get you much as a European resident - no lounge access, etc., plus QF's redemption rates are nothing to shout about.

On the other hand as a European resident (lower threshold than UK/N. America residents) you'd earn more than enough British Airways tier points (TPs) for Silver status (Oneworld Sapphire - the middle tier) which comes with lounge access and other benefits that you'd be more likely to use as a EU resident.

However, to reach BAEC status you have to fly at least 4 segments on BA metal, so if it was me I'd put the miles toward BAEC membership, then when you return to Europe figure some inexpensive way to accumulate 4 BA flights (some very reasonably priced routes in J to/from LGW for example) and you'd be sitting pretty with BAEC. BAEC has some decent redemption alternatives including miles for upgrades that are fairly generous.

If you had time before the Oz trip, doing the BA segments before the longhauls would (I believe) increase your mileage yield as you'd hit status during the trip, thereby earning bonus miles from that point on. Others may correct me on this, however.