Additional data point: USD410/EUR365/GBP325 on FCO-ADD (from an H fare).
Quick question: the page where you enter credit card details stated "Kindly be informed that you have to verify your credit card used to purchase your economy class ticket before submitting bids if you are already contacted to do so".
Is that supposed to mean that I am expected to use the same credit card as I used for the economy booking? I used a different credit card and it seemed to accept it for submitting the offer (although obviously I won't know whether it worked until the offer is accepted and they attempt to debit the card). I also submitted the offer in GBP even though the original ticket was in euros. Let us hope that neither will throw a spanner in the works.
The text on the offer submission screen also listed as one of the advantages of upgrading: "Lounge access at Addis Ababa Bole International Airport". I take it that is default standard text and that I will in fact have access to whatever departure lounge they use at FCO rather than on arrival at ADD.