From some research and from the attached diagram it appears that the crew of a Lancaster would have stowed their parachutes before taking off. Given that this means that the crew had time to clip on their parachutes (most likely the chest mounted variety) it would appear that the crew had time to do this.
As Richard Curle was found with parachute attached I would theorize that the aircraft was most likely hit by flak and the pilot attempted to gain height to allow the crew to bail out. Given the parachute is attached it's almost certainly not the case that the aircraft ditched (no point wearing a parachute when ditching in the sea).
This is intriguing information but also incredibly sad as it could be the case the crew did exit the bomber but were lost at sea. Would crews voluntarily bail out over the sea? That is a very interesting question.
As and when information is found I'll post to this blog.