“They order the toasted cheese sandwiches blithely, “ (audio)
(by Edward Field, from writersalmanac.publicradio.org)
The reader, Mr. Garrison Keillor, sounds to be pronouncing ‘blithely’ as /blaɪθlɪ/. Is the word pronounced only as / blaɪðlɪ/ in UK? His pronunciation is not found in both OALD and other oxford dictionary online.