Thank you for the replies. I decided to book a flight back from Brazil using Aegean miles on Avianca. So, I should not have a problem with getting into Brazil and I hope I don't have anything but a good experience with Avianca, but that's another future tale!

Brazil does not require a return segment or onward out of the country, only that you can show you have no intention of remaining there and have sufficient money for your stay. I am sure I do not fit the profile of some one escaping penniless to Brazil so that did not worry me. What did worry me was being rejected by the checkin agent. In 2013 flying LAX - NRT in JAL F they did query the single ticket and I needed to find the email for my return to UK before they let me on.

Thanks again.