Welcome to FlyerTalk, britoz. Lots of great advice here. I cannot recall if the 26th of July was affected by weather related ATC restrictions but it does appear that BA1407 left MAN fifty minutes late (at 20:25) and picked up a further 14 minute delay en-route, arrived in LHR at 21:34. Soul destroying isn't it? So on the balance of probabilities the extended flight time suggests there were factors at play that exacerbated your initial delay. BA’s SYD flight left LHR at 22:00, 25 minutes late (assuming BA15 was your onward flight).

So it sounds like you will be entitled to compensation under EC261 - but if 26 July was a snotty weather day, BA may argue there were aggravating circumstances outside of its control that caused you to miss your connection. Do let us know how you get on.