Hey Malcolm,
Im using the Chrome inspector tool (F12 on a PC). In the screenshot below, I've found an email and clicked into the "Preview Email" view. In this view, your variables are rendered out into the code. The catch here is that your images may use a different proxy path (url) so those all need to be updated still which can be a little bit of leg work.

Walk thru:
1) Right click in the margins (lt gray) to bring up the browser menu in Chrome and select "Inspect" (or just use F12 on a PC).
2) click the selector tool in the top left of the Inspector and then click again into the left margin -- this'll take you to the <body> tag in the code. Just a few lines up from there, you'll find the <html> tag which has the translated code (no variables).
3) click on the <html> tag, then right click to bring up the inspector menu. From there choose "Copy" > Copy Element to add the <html> element (and everything inside it) to your clipboard.
4) paste this into your favorite code editor, replace the image paths and do a happy dance 
Let me know if you run into any issues with this approach, happy to help out more if I can.
-Dave