When you watch an on-demand programme and don't get to finish it, then we keep a note where you left off so you can jump back in and continue watching from that point.
If you started watching on the Web site or on the Android site, then any unfinished shows will show up on you homepage under the Continue Watching heading.
Or you can just navigate to the episode you want to continue watching - clicking on it - and you'll get the option to resume watching.