I completed the exercise over the weekend and submitted it. I received a response the following week with no feedback other than Cookpad were no longer interested in continuing the interview process. Despite me asking, I received no feedback AT ALL (why I had failed, on what grounds etc.). This was terribly disheartening. I was simply looking for some constructive feedback so I would be better prepared for my next interview - it would have 5 minutes of their time, perhaps less.