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You will be in T3 so the BA Galleries lounge will probably be the best pick. Alternatives include the CX lounge and the AA lounge, which is of course awful, can be be useful if it is quiet while the BA lounge is busy before the two QF departures.
I'd go with BA. The noodles at CX are a tad overhyped, but this possibly does depend on who is in the kitchen at the time (operating the microwave??). The CX showers are good though (same facilities for J and F). Food options in BA F and J lounges are the best at T3. Only bother visiting AA for a full-on lounge run.