The /əʊ/ diphthong is spelled <oCe>, <oe>, <oa>, <ow>, and <eau> in beau. The /ʊə/ diphthong is spelled <ure>, <oor> or <our>.
This is a contrast between two diphthongs with different starting positions and direction of movement. In fact they form an almost perfect reversal; record one and play it back reversed and it will sound like the other (which is a very good way to persuade students that /əʊ/ is a diphthong). It is not a problem for learners.
The density figure is 1.9%. The set makes 11 semantic contrasts giving a loading of 55%.
beau boor beaux boors bow boor bows boors bone bourn bones bourns goad gourd goads gourds lode lured low lure lows lures lowed lured mode moored mow moor mows moors toad toured toe tour toes tours tow tour tows tours
John Higgins, Shaftesbury, December 2009