I just got a DUB-LHR-SIN-SYD-SIN-LHR-DUB for £1011 in WT+. I thought that was great value compared to the ex NCL price of £3.8k! In fact, the cheapest economy ticket from NCL was around £1.7k with some suspect airlines...
OP- there are MFU seats from WT+ to J on the BA11 LHR-SIN available right now, I literally just checked to try and MFU into J myself on the 14th.