Many thanks to all of you for your helpful comments. We have now returned to the UK and can report that our day in Rio was a resounding success! We followed Falcon/Hermes’s advice, staying at the Marriott at Copacabana and using a yellow taxi for the transfer from the airport to hotel. There was absolutely no hassle in using yellow taxis for trips around Rio – they were not at all expensive, especially for a visit to the Jardim Botanica, which provided a tranquil break from the bustle of the beach area. We didn’t want to do the usual tourists sights (Sugar Loaf etc), since we had visited those as part of a cruise tour several years ago.
OK, being a Marriott Gold Member also helped in providing a great ocean front room and access to the Executive Lounge, which we were able to retain until 9pm. Once again, using a yellow taxi back to the airport was no hassle. I concur with Falcon in that Terminal 1 and the BA lounge at GIG is still a disgrace – such a contrast to the spacious new TAM lounge at GRU which we used for the outgoing flight and can thoroughly recommend.