As an SL who somewhat regularly flies in PY on a mix of R and T fare codes on flights between HKG/LHR in peak season, pretty much none. Don't get your hopes up. Also, the fare class you are booked in makes little to no difference when it comes to op-ups. The only thing you could do to perhaps improve your chances is do OLCI right when it opens up.

I appreciate the quick response. I've been flying CX as an SL mostly on Y and on a few occasions, J, but I managed to snag a good deal on PY and thought of the possibility of getting bumped up to J given the fare class I booked.

Based on greeting by name of DM and GO in the PEY Cabin as observed by myself in my commute between YYZ and HKG I would say ZERO.
Op-up are status based

Those routes regularly have 30 Diamonds+OWE. You’re better off begging them to use miles to upgrade.

They used to upgrade a lot of SL international students (myself included) from Y to J long long long time ago. Are students the exception or have they fallen down the pecking order now?

It's not an exception. I'm also a student and I think the reason why we SLs get upgraded a lot is because we are flying during peak times for school (start and end of term), so the plane is full of college students etc. Most of this demographic don't care enough to optimize and get status, so we are at the top of the op-up list. I recently snagged an op-up from PEY to J from HKG to JFK and the flight had a lot of college students.

I would suggest there has been a rise in fellow students who have become GO members. On one particular flight from LHR-HKG last December, I recall 5 or 6 greetings being given out to others who also looked like students.

The LHR route has many students who are SL/GO, some are even DM. I am relatively young and have gotten weird looks from my neighbours after the greetings, especially in short haul Y by myself.

I wish it was a thing that they op-up students. I would enrol back into full-time education for this perk. Many students fly so often that they get status and priority when it comes to upgrades. We do need to remember that outside of the FT world, even SL is not that common.

Out of interest, does CX publish any stats w.r.t. its members' demographics? (numbers, by age, by location) etc.?

On the other hand, if students attain their status by frequently flying as a student, they'd probably reduce flying by quite a bit after graduating and thar might not be the airlines' top priority in terms of customer retention...
It'd more likely be a batch of students every year which come, then go after a few years

Don't think so, at least not recently. You'll hear different numbers but unless you work for CX or know someone high up, at best it's an educated guess.

Always thought it was a "get em while they are young" sort of tactic by CX, giving access to fancy lounges with champagne, priority baggage/check-in, upgrades, etc. It's quite addictive when you're young. Been keeping my status since I got it years ago as a student and always prioritised CX for work (and personal) trips when available.

I’ve a return flight LHR-HKG in J in 6 weeks. I enquired as to the cost to upgrade 1 leg to F, and was given a price of £5033 GBP - 51,200 HKD….

Is it possible to Upgrade using Avios?

Looking to book HKG-HKT return. £250 in Economy and £1000 in J so would prefer to try and use Avios.

My assumption is that any availability would just show using the standard Avios search on the BA Website?

If this is not an option - what would the next best method to be rather than paying the full cash fare (Bid?)

I was looking to see if I could upgrade to Business class on an R class ticket from ICN-LHR via HKG. From what I remember, the Upgrade award used to be distance based. This ticket that I currently have would cost 42000 miles for an upgrade (ICN-LHR via HKG is less than 7500 miles in total distance). It said 42000 miles was required when I checked last month. Now after checking today, it says 56000 miles (14000+42000) is required. It seems that they are charging both flights separately. Has there been a change in policy?

No. Not possible.