In advance of this I will state that a "Direct Flight" is not the same as a "Connecting Flight".

My opinion is still that the flight from LHR-SYD is late and on that basis compensation of €600 is payable based on the "Sturgeon" ruling (3+ hour delays provides for cancellation compensation).

With Gahan a flight from Manchester to Dubai was delayed by nearly 4 hours, meaning the passenger missed their connecting flight and so arrived over 13 later than scheduled. Consequently, a claim for delay compensation against Emirates was made. The Judge held that the claimant’s flights were to be considered as separate units and that since the claimant’s second flight fell outside the scopeof the Regulation 261, the claimant was only entitled to €300 EUR compensation in relation to the delay to her flight from Manchester to Dubai, rather than €600 EUR sought for the delay into Bangkok. The claimant then sought, and was granted leave to appeal.

So in that case there was a late inbound flight and a connecting flight with a different no - there is really no relevance to the OP's situation.

<More coming>