Complex sentence: Several commercial mushroom ketchups were produced in the United Kingdom; some of the brands included Crosse and Blackswell's Mushroom Catsup, Morton's Mushroom Ketchup and Geo Watkins Mushroom Ketchup.
Split into simpler sentences: Several commercial mushroom ketchups were produced in the United Kingdom. Some brands that existed in the U.K. include Crosse and Blackswell's Mushroom Catsup, Morton's Mushroom Ketchup and Geo Watkins Mushroom Ketchup.