Working With Flows: How Do I Access an Assigned Value Outside of a Repeat?

I have a Data Store with values like this:

attendees[1]
   first_name: "Fred"
   last_name: "Bloggs"
attendees[2]
   first_name: "Jane"
   last_name: "Smith"
attendees[3]
   first_name: "Mary"
   last_name: "Robertson"   
attendees[4]
   first_name: "Paul"
   last_name: "Peterson"   

I want to loop around these in a flow in order to create strings such as:

Jane Smith, Mary Robertson and Paul Peterson
Dear Fred, Jane, Mary and Paul...

(and other similarly non regular combinations)

Which I then assign to a variable outside of the flow.

I’m really unclear about how to do this!

My starting point is shown below… but the resulting variable description_booking_names ends up being null.

So another way of asking this is: In a flow, how can I use an assign within a repeat and access its value outside?

Can @George, @patrick or anyone else please tell me how I can do this?

Thanks!

Antony.