Maybe they've left it like that so depending on audience reactions they can bring Len back and tell us he survived and make more programmes with his character intact? I read somewhere that people are suggesting how to continue the series with The House and storylines based on the occupants and their past and how they got to be as we saw them-including Len. Sad copper wasn't he?
Loads better than Broadchurch

Watching that was like wading through treacle. Eight episodes of that and only three of What Remains? Makes no sense to me.