All I can say to all of you in this situation, do not lose heart and do not give up. HUACA HUACA HUACA

I finally got lucky with an excellent agent at the BAEC, who rebooked me free of charge onto the BA flight to LHR, then on to TXL. There would normally have been a lot more Avios and taxes to pay on this route. But it took a bit of determination to keep calling back every few hours until I got somebody who was prepared to deal with it. I had already booked a backup ticket with Avios on Royal Jordanian via AMM and I got the agent to cancel it as we were just inside the 24 hour booking window.