If you have a stopover in SIN each way (or change planes instead of staying on the same flight #), you'll earn 30+40+40+30 SCs, otherwise if your BP reads "Sydney to London" or "London to Sydney", it's just 60 each way for Discount Y etc etc (same as QF). Points will be the same as QF on this route (see the fine print down the bottom of the BA page on the QF site that confirms this).
When is the OP going, the demise of the JSA March 31 will see the earnings change to 0.25 for discount economy, as the allowances for 1.0 on the London via Asia routes are part of that agreement.
AFF Supporters can remove this and all advertisements