Advice on business class SQ BNE-LHR upgrade?

[ProfessorLesser]

Hi there, apologies for the newbie question.

I'm thinking of flying Business BNE-LHR either June or November (I know), but only have 77k Krisflyer miles - at best, I'm only going to be able to take the sting off, but want to lessen the pain as much as possible! Award flights are barely discounted with this many points, but I'm having trouble seeing what I can do with an upgrade.

Assuming I buy Premium Econ seats with cash, does anyone know what I'm looking it in terms of mixing miles/cash for the upgrade cost? The cost in miles alone is 120k which makes me hopeful that 77k could make a good dent in the difference. However, there's no calculator for this - the only way to know is to actually buy the flights and try, which could be an expensive mistake! Additionally, SA customer service were completely unhelpful, and Flight Centre say it's beyond their remit.

Can anyone here advise or at least point me in the right direction?

Much obliged!

 

[Quickstatus]

Welcome @ProfessorLesser

Have a look here
Flight centre is correct - this not something they would get involved in. But then I would not want Flight Centre to be involved in any of my travel itineraries.

To upgrade with points your starting fare needs to be either a Standard or Flexi fare. Lite or Value fares are not eligible. Also note that the upgrade availability is not guaranteed