Using ITA Matrix (or Google), you ought to be able to search into most of the usual suspects (including LHR) but return from BER, AMS, CPH.
There appears to be SYD-HND-LHR//AMS-LHR-HND-SYD departing early June / returning mid/late June ~$6,145. Ive not checked if that’s bookable directly on JAL. It usually is but the multi-city search isn’t great for telling the total price until the end.