Interestingly I've been wondering what the process is on CX too.

I'm booked in Y (V class). I've looked in Manage Booking and started a dummy change my booking, but that doesn't give you the option to change class, just the flight or move up the Y class categories to a fully flex Y ticket.

I'm guessing I'd have to ring up and they'd quote me the the current PE fare, plus the £100 change fee, plus I'm guessing a telephone service fee?

I did try searching on the CX site and found this link,

Terms and conditions - Cathay Pacific United Kingdom(HTML, 51025b)
...booking change. No further upgrade by cash, Asia Miles or otherwise will be entertained after Enhance upgrade has been successful offered...be entitled to any further upgrades for such flight whether by cash, Asia Miles or otherwise...

http://www.cathaypacific.com/cx/en_G...onditions.html

But when I pressed on the link, I got a 404 error:

We can't find the page you're looking for.
This page could have been archived or the address is incorrect. Let us help you get back on track.
(Reference no.: 404)

I'm guessing this is the bid system talked about above.

Do CX ever proactively offer paid upgrades, either online, at check in or at the gate? Or even on board? I say on board because my very first CX flight LHR to HKG I got stuck next to a person of size. On saving grace was that it was an exit row so I could get out easily. But after 12 hours of sitting contorted I would have gladly paid to move. However it was a pre-xmas flight so I knew chances would be slim of spare seat.