WooCommerce Plugin - Adding An "Out of Stock" Image

[andoverit]

Theme: Agency 2.0 on Genesis 1.8.2
Website: www.ladida-andover.com

I would like to be able to add a red circle with "Out of Stock" on any products that are out of stock, similar to the green "Sale" offer that is built in to the plugin.

See http://www.ladida-andover.com/shop/black-slatted-bench for an example.

Ideally I'd like to add the red one to the opposite side to the green one so that both could show if required.

I have to admit I am at a loss as to where to start although the logic is obviously along the lines of "If Product = Out of Stock Then Add Red Image to Product".

Any pointers / clues / pages of coding welcome!

I'll also feed it back to Forum Members once have cracked it.

Thanks