You can actually grade a dog food - there are various versions around but I have used this one a few times

here is the scoring mechanism to rate the food you are feeding {although originating in the US, it applies to UK producers too}:

You will need your kibble’s list of ingredients, as found on the label (or sometimes reproduced on their website). This is intended to help you evaluate the ingredients, but the food has to be appropriate for your dog. If your dog is allergic to an ingredient, or doesn’t like the taste, then it doesn’t matter how good the kibble is – it isn’t appropriate for your dog. Whatever you pick must also be appropriate for your dog’s breed, life stage, and lifestyle, so check the guaranteed analysis, first.

You have a right to expect good ingredients, so start with a grade of 100.