First, welcome Second, congratulations on an excellent first post which I hope many other newbies will find in future too - it's a great summary and you've clearly done your homework! ^

Yes, basically, it's that simple in theory! The confusion comes on the AmEx voucher. In short, this basically doubles your miles balance for straight redemptions (i.e. paying for the full trip in miles only) allowing you to take two people for the price (in miles) of one. It can only be used on straight redemptions not upgrades, and only on BA operated flights not any codeshares. In your case, you're spot on, 100,000 miles + voucher would get you two free (except for taxes/fees) World Traveller tickets to Australia ^ Note BA don't fly to NZ, so you'd have to arrange/pay for/use extra miles separately for tickets from SYD to NZ.

Caveats/answers:

*) The voucher comes normally right away after you hit the spend on your last AmEx statement. Under the current rules, you have one year to spend £10,000 (from the date you get your card). If you do it, you get a voucher. Either way, the process starts again the next year (based on the same date again) - spend is not carried over these days...but if you keep spending £10K a year, you get one voucher a year.

*) Australia is very hard to redeem for in premium classes. I'm not sure about economy, but you will probably need to book as far in advance as you can to secure the seats once you have the miles. You will need to find flights with 2 reward seats open on each leg for both of you (you pay one lot of miles + voucher, but need 2 seats open). Re point (4), this refers to the minimum time you can book, not maximum (which is ~1 year).

*) You may want to follow the Tesco thread for hints on racking up the miles super fast (like buying 10 tonnes of Palmiers and 30 tonnes of beef or something...).

*) Also, any flights you take in the meantime on BA/oneworld, be sure to credit to your BAEC accounts - every little helps. As do other 'offers' (e.g. car hire, hotel stays) or schems (e.g. BA Wine Club if you drink wine enough!).

*) Finally, you can also buy miles from BA at up to 15,000 per account, per year. If you're "just short", you may want to consider this. If you want to buy 30,000 miles, you and your girlfriend could consider a househould account and 'pool' these miles in one effectively to reach 100,000 faster...

These are very quick points/references, lots more info is in the ULTIMATE sticky thread and others (e.g. Tesco thread, but I don't follow that).

Good luck

Phil