Orders cancelled twice! Simply not good enough!

First order was fulfilled satisfactory. But alas, further two orders were cancelled due to the supplier being out of stock. There was no notification from Avo about this, and only discovered this by accessing the site again and tracing the reference numbers. 'Your order has been cancelled."

Should an item not be available to purchase then the website should either not display the item or advise that it is sold out prior to completion of the sale. Most frustrating!