So, lets start with the labelling laws. Before December 2014 ingredients were allowed to basically be a straight list of all the ingredients listed from the the ingredient with the highest percentage within the product to the least with no need to point out any allergens but manufacturers could put allergy boxes pointing out allergens or may contain warnings.
From December 2014 new labelling laws were introduced, if any of the 14 main allergens were present in a product they HAVE to be highlighted within the ingredients whether written in bold, a different colour or underlined, it just has to stand out from the other ingredients. The 14 allergens which fall into these laws were Cereals containing Gluten, Milk, Eggs, Peanuts, Nuts, Soya, Fish, Celery, Fish, Mustard, Sesame, Sulphur Dioxide, Lupin and Molluscs. All in all this change SHOULD have made labels easier to understand, but another change in the laws meant that the may contain boxes were no longer allowed, although at the manufacturers discretion they can print may contain warnings on, but they don't HAVE to, so be aware that any products without a may contain warning could be a risk from cross contamination but may also mean they are not since they don't have to legally print that information.
Even though these laws should be easy to follow, lets see it in practise.
This is the one that gets most people I think. The ingredients show there are no allergens within the ingredients,
Hopefully this has helped you understand your labels a little bit better, once you remember to check for the bold (but ALWAYS double check, I have seen manufacturers make errors and forget to place a word in bold before) and check for any may contain warnings you are on to a winner.