Export to Fixed Layout Epub
Then change the epub extension to .zip
Unpack the files to access the HTML files.
But there's no way to go from InDesign to Photoshop easily, I suggest rebuilding in Photoshop to their spec.
You could export each InDesign layer to a PDF then open each of those in photoshop and then relayer them there.
Export as PDF/X-4:2011 and place it layer by layer in Photoshop. This can be scripted.
Since CC 2015 you can use CC libraries to exchange content between ID, AI and PS. Even text styles and life text can be exchanged in a limited way under narrow circumstances.
Thanks Eugene & Willi - i ended up rebuilding in photoshop as exporting wasn't working out for me - when i have a bit more time i'm definitely going to give this another go though! Cheers!
If you are using OSX this AppleScript will do it:
This thread explains the usage. The InDesign layers can be optionally exported to PS as smart layers, which will give you some limited text editing capabilities