There seems to be restrictions on MFU based on where the itinerary is "booked" and the departure city.

So if I booked a round-trip itinerary that is UK-US-UK (to take advantage of the current ex-UK sale) and I live in the US, does this mean I cannot MFU my flights? I did not log into my BAEC account when I booked the itinerary and used my AA FF#, entered my US address and used my US credit card to pay for the ticket. There is no CW upgrade inventory at the moment, but I was hoping for upgrade inventory to open up closer to the travel dates.