Thankyou, John. In the end, based on the advice I received in my phone call to SQ, I did it online and although I didn't achieve all I wanted, I am happy to settle for what was possible. What made a difference was that, with effect form 1st June, upgrades from Economy to Premium Economy are available and can be done online using points, provided PE seats are still available on the required flight. And the whole ticket must be booked first in Flexible Economy before doing so. Unfortunately, SIN-LHR (SQ 322) was not available in PE on 2 June, but I did manage to securea seat on the upper deck of the A380 for that flight. For SQ 321 on the return it cost me just 27,625 KF miles to upgrade so I didn't need to transfer more.
What was surprising was that the rep on the phone told me that SIN-MEL (SQ 227) on my return date was waitlisted, but I found it was still showing as available online. I took that as an indication that it was becoming full, and I therefore proceeded with the whole booking straightaway.
I did note the following in the Additional Information section at the end of my upgrade notification, which may be something new:
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[TD="colspan: 2"]If changes to your booking are not made online
Please note that any changes to your booking, such as change of itinerary, change of travel date(s) and/or change of passenger name(s), made through KrisFlyer Membership Services, Singapore Airlines reservations or ticket offices will mean your booking will no longer be eligible for the online redemption booking discount.
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