The CW headphones are noise-cancelling, just not the best example of them. BA's aircraft with IFE have 2 sockets, the standard 3.5mm jack and the noise cancelling jack, or you can use a headphone with its own noise cancelling logic that uses the 3.5mm jack.

SIN on the A380 almost always leaves from T5C, but in theory it could be from A (bus) or T5B (bus or one gate). But I would guess 99% leave from T5C. That's kind of an exception here, very few services have dedicated gates or terminals anywhere in LHR, just Aer Lingus in T2 as the biggest exception.