Not sure if this is allowed but here goes....In case anyone was looking to buy a wedding dress box I have found a 10% discount code for the empty box company, HJ11 gets you 10%off, which more or less covers the cost of delivery. The price is recalculated at the bottom of the page if you think it hasn't worked (like I did for a while!)
They do travel boxes too that are sized for hand luggage allowances which is very handy