Some useful links:
We used Skyscanner to find the cheapest flight. To our delight the best fare was with Korean Air. Three of our friends had taken the flight from Auckland to London (and vice versa). Each had been treated to a free stopover, including free hotel and free transport and free buffet dinner, free buffet breakfast and a free voucher to purchase lunch at the airport. We were a little sceptical ourselves. Surely it was too good to be true. We wondered whether we would be so lucky. But we discovered for ourselves, that everything was genuine. The services including customer service, were superb. I could not speak highly enough about this free stopover. Will we flying Korean Air again? Most definitely!