Returning 2 swapped phones

[WR60]

I recently arranged to swap 2 phones . One packaging box + one label was received to return the 2 phones . 
one new phone has arrived and I have 14 days to return it but the other new phone looks like it will take another 2 weeks to arrive . Should I wait to return both phones together , exceeding the 14 days , or try and get Sky to send another returns box and label ? Any guidance would be appreciated . 

[caesarome]

If you have only received the ackaging to return one of then I would contact them about this missing ackaging and to ask them if they can extend the 14 day return window due to the packaging not arriving.