I live in Australia and try to use the Amex 241 voucher for trips from the UK to Australia in J because it gives lots of flexibility. The main issue is that BA only has one route - the BA15/16 through SIN. They generally only release two J seats on each service. This happens 355 days out, so I book them at about 1am UK time just after they are released - it seems the only reliable way to book them unfortunately.

If you are not tied to BA metal, then QR often have availability, or BA to HKG and CX onward from there.

I get creative by booking a redemption to KUL/SIN/HKG using BA and the 241 voucher, and then paying for the final eight hours or do seperate redemptions on a suitable carrier.

J