Weetabix has a long history with Lego. Their first release in the early 1970's was a castle. In 1976, they released three town sets. With the addition of posable minifigs in 1978, they released one large town set, later adding two smaller sets. All of these sets were available by collecting coupons on the back of breakfast cereal boxes in the United Kingdom.
Pictures found at the website of Clark Stephens: http://www.isodomos.com/Lego-Sets/Weetabix.html