Although the informative and well-written explanation regarding British mustard could stand alone, I feel as a mustard-loving American, I am compelled to add my two cents. In aisle 8 of my local grocery store, there exists a plethora of mustards to choose from besides the stereotypical cheap yellow stuff.
I know because I just shopped three days ago and stood there, amazed at not only the quantity of various types, but the cost per pound. My favorite happens to be inglehoffer ORIGINAL Stone Ground whole seed mustard with No Preservatives, which comes in a 10 oz. (283g) pleasingly round clear container. It is Certified Gluten-Free and Gold Medal Winner in the Napa Valley World Mustard Championships. The mustard is from a family owned company since 1929 and is packed in Oregon, USA.
Ingredients include: water, mustard seed, white distilled vinegar, red wine vinegar, white wine vinegar, garlic, spices, xanthan gum, turmeric, citric acid, artificial and natural flavors, annatto.
The men in my house hate this mustard, but I sneak it into soups and they are none the wiser. I purchase the alleged all-American-slathered-on-hot-dogs variety for sandwiches, as we rarely eat hot dogs, except at family barbeques.
I have used the yellow stuff, mixed with honey, for dipping cooked, breaded chicken. However, if I wanted, I could purchase honey mustard in aisle 8, probably 10 different brands or more. There is also light brown mustard, mustard with wasabi, mustard with horseradish, mustard with Jack Daniel's, you get the mustard idea.