Ompah ompah ompah is exactly right for 3/2, Dazbo. There are three minims(main beats) in the bar of a 3/2 hornpipe, and each minim is divided into two crotchets(om and pah, as it were). 6/4 would be ompahpah ompahpah, quite different. (6/4 is not really much different from two bars of 3/4).
For excellent examples of English 3/2 hornipes, may I recommend "The Beaggar Boy of the North", Greg Stephens and Crookfinger Jack, Harbourtown HARCD051. It is a recent CD reissue of the 1978 Fellside LP of NW English instrumental music, without which no decent record collection could be considered complete. For a more recent example of good 3/2 hornpipe playing, Eliza Carthy and the Ratcatchers play a very splendid Cobbler's Hornpipe on "Rough Music".