Originally posted by Attitude23
I believe (thats because somebody told me[:I])the reason you will of been able to do miles upgrades at MCO and not at LGW is because the staff at the non-uk airports aren't so aware of whats allowable with each fare so you are more likely to get away with it where are the UK staff no all the restriction and therefore won't allow it
Hmm, yes & no - whilst that can be true, I've found that staff at outposts will more than likely ask their supervisor/manager whether they can allow an upgrade, and then it's down to the supervisor/manager as to whether they know the fare codes. I've definitely seen them look up the fare code to see whether it's upgradeable, and then refuse on that basis.
Originally posted by tallprawn
It may have been the case that VS would need to move people because Y has been oversold. It could be that they will accept cash rather than moving people for free regardless of being booked into the lowest fare bucket. 
Indeed. With the exception of mistakes, VS will pretty much only accept upgrades on non-upgradeable fares if it's suitable to them operationally. Likewise, even airport upgrades on upgradeable fares can be refused if there's no reward availability and it's not suitable to VS operationally.
Recently I saw an example of how VS needed to op-up folks in Y/PE (so there was an operational need), but wouldn't accept miles to upgrade my N fare - so it's not a certainty by any means.
Cheers
Michael