Thanks to daneditor's suggestion to use dialogue from 'Star Wars: The Interactive Boardgame' and darth_ender's kind uploading of said game. I've been able to create new dialogue for Vader that is unique to this scene instead of re-hashing lines from elsewhere in the OT. Thought I'd show it in colour as you can already see how the BW version looks anyway, on my Vimeo channel.
The scene is much improved, thanks guys!
Click the image below to see the video:
...also a download link of the completed first hour may be coming to galaxy near you very soon!