Airport upgrades went up back in July to double that of an online upgrade.

On occasions an award seat may appear around 24 hours before a flight which you can then do an online upgrade (as I did for my SFO-DOH flight in July).

I tried to help a friend upgrade the other week around 24 hours before his fight. There was an award seat available but it didn't show up on the online upgrade. After he checked in at the airport (in DOH) he was quoted double the Avios to upgrade. The award seat was still available so he just purchased a new flight and because he had already checked in it didn't affect his connecting flight or return flight either based on the fact he didn't actually take the original economy flight that was paid for!