By my calculations 10 weeks from the end of February was up yesterday so this morning I was on the phone to Qantas Money. They've said it is a Qantas promotion and they have to pass my inquiry onto Qantas for actioning, Sounds like this is going to be a fight.
Interesting change on the conditions for that offer:
Qantas points will not be earned on the purchase of gift cards or orders redeemed with a gift card.
Did you look? I looked at 3 random dates in April/May and all had availability for 2 on either QF or JL. If you are WP you can also call to get seats released.
If you don't have access to the premium team try calling during a busy time and opting for the call back. I've had 100% success rate of getting called back by them and it's ridiculous how much better they are.
I had a flight booked in J and the plane was changed to one with only Y. I called and was rebooked into business on another flight even though there was no award availability. Call them and see what they will do. If you can get the Australian call centre that will make it a lot easier...
You're over 35000 miles, according to GC Mapper it's 35614. If you go straight from BER to LHR you'll get under. Don't worry about BA surcharges on Europe flights, they aren't much. It's only the long haul ones where they sting you.
I tried to do this twice, the first time they tried telling me it wasn't a reward booking and I'd have to pay ~$12000 to make a change (they obviously wanted me to pay for all of the flights) and the second time they took forever (at least 2 hours) and then ended up telling me I had to call.