I have been told that the commandments are given in order of importance, why is it that "honour thy father and thy mother" is more important than "thou shalt not murder"?
Whoever told you that is wrong:
http://www.vatican.va/archive/ccc_css/archive/catechism/p3s2.htmThe unity of the Decalogue
2069 The Decalogue forms a coherent whole. Each "word" refers to each of the others and to all of them; they reciprocally condition one another. The two tables shed light on one another; they form an organic unity. To transgress one commandment is to infringe all the others.30 One cannot honor another person without blessing God his Creator. One cannot adore God without loving all men, his creatures. The Decalogue brings man's religious and social life into unity.
St. James chapter 2
http://www.drbo.org/chapter/66002.htm"And whosoever shall keep the whole law, but offend in one point, is become guilty of all."