Posted: 15/06/2013 at 09:37
Would it not be more constructive if you took a sample (or the remains of the bag) back to the store and complained directly to the store manager? If nobody make a formal complaint nothing will be done about it.
I think you would be very lucky to get anything for consequential loss as the store cannot have knowledge of your gardening competence, but you should have your money back and a voucher. I did a couple of years ago.
Also mention that you use messageboards, as the companies don't like adverse publicity.