Since they were not suited for combat, they transitioned to supporting clandestine operations where, to quote the Royal Aviation Museum of Western Canada,
To give it the long range it needed, the aircraft had to be lightened by removing all unnecessary equipment such as guns, armour protection and excess radio equipment, retaining only the radio/telephone for communication with the ground.
It appears that they did have radios, not sure about how they were used. But if you look at the video in the linked page at about 2:33 the pilot appears to be wearing a helmet with built-in headset and a face-mask type microphone. At 6:19 the rear crewmember looks like he is wearing a mask as well.
This is the same aircraft that features prominently in Code Name Verity by Elizabeth E. Wein.