Pictorial history of BOAC and Imperial Airways by Kenneth Munson has"at best,the Lancastrian could carry only 11 seated passengers,but since bunks were needed on the marathon journey in the unpressurised,unsilenced machine this number was reduced to six"
That was on a 63 hour flight to Sydney.
BOAC by Charles Woodley has a description of the passenger cabin.There were settee benches along one side of the cabin,converting into sleeping berths with fold down upper berths above.