Drupal Rooms Show Booking Unit Name in Confirmation Email I have had a drupal rooms site running for a few months now, and the client has come back to me asking for the selected room to be shown in the confirmation email sent to the customer.

I have had a look through the available tokens that come with rooms, but there isn't one to display Bookable Unit Name, probably because it can be a multiple value field if more than one room is booked.

Or even a way to display the Rooms Unit name in the line items, then that would print in the notification email under the line items token?

I have gone to products > room products > manage display > line items, but there is nothing there to display the name.
You could create a custom token to pull that info in. 
Hook_token_info is the hook that makes a token available.  

https://api.drupal.org/api/drupal/modules%21system%21system.api.php/function/hook_token_info/7

While hook_token is the hook that actually replaces it.

https://api.drupal.org/api/drupal/modules%21system%21system.api.php/function/hook_tokens/7

Since it's a multivalue field, you may need to include a numeric operator on the end (e.g. node_room_field_room_number:0) for the delta on the field.