Oceania booked us on Virgin from Heathrow to Miami in December and British Airways from Rio de Janeiro back to Heathrow. We were told we could not choose our seats until flights were ticketed. That turned out to be partly true. Good old Virgin not only allowed us straight away to book our seats in Premium, it was also free. BA made us wait until ticketed by which time the best seats had gone and charged us £91 to choose what was left.