How to create a new checkout session

[strelitzia]

I've been making some modifications to the save for later module, but notice one further thing that I feel should be addressed.
If a user has saved for later items, they can't simply click to move it to cart and then checkout if they didn't already have an item in the cart.
This is due to there being no valid cart session.

I did try using zen_session_start(); triggered when they click the button to move the saved item to cart, but this didn't seem to make any difference.
I'm assuming it's somewhat more involved than this.

Any pointers would be gratefully received!

[lankeeyankee]

edit: saw you posted already in save for later thread