Replacement PSU now received.
Since receiving returns label and shipping it off to Corsair at the end of last week, things sped up. They received the faulty PSU on Monday and dispatched replacement same day which was received the next day. There was more communication from Corsair reps on each stage of the process.
Corsair, you have redeemed yourself. This is how customer service should be. Let's hope the new PSU can uphold your reputation.