Hi Lisa, the Mix It Panelled Wardrobes are exclusive to John Lewis & Partners and the best way to get hold of them is to go to the relevant page at johnlewis.com and enter your email address where it says 'email me when back in stock'. This may seem like a flippant response but I don't want you to miss out and this really is your best option.
I don't know what the situation is currently with the Mix It range but I do know that some other ranges have sold out again as soon as they come back into stock from the email list alone.
Best wishes