I think its been said numerous times, if something has failed/broken then it is not the manufacturer you go back to, its who you bought it from you take it back to.
I would argue that the product has broken under normal use within a reasonable amount of time and you are entitled under consumer law to a replacement or refund from the shop. It is then the shops job to return that product back to the manufacturer.
I have in the past writen/emailed a manufacturer when I have found fault with a product to voice my concerns and to offer my opinions as to why it failed if it was a design fault and how the product could be improved. Constructive critisism is usually received well rather than just telling them the product is crap, as some seem to like to do.