Scapegoat, take the wheels off, put something through the axles and kind of hang them so they are free standing.
Then kind of pluck the spokes, make sure you do it in the same position on all the spokes, do any sound grossly out of tune compared to others?
Do you have any friends who can build wheels?
Hmmm, some slack as a bag of knackers, others taut. Had them checked by LBS who used a gauge to show me how inconsistent they were, and how some are nowhere near the recommended tension.
Weighed up my options and got a quote from the LBS guy who told me that he would rebuild them for me for 50 quid. He told me the build was so poor he would have to more or less start again. He quoted me £360 for a new build in the same spec, so paying him to true them works out cheaper than sending them back to the original supplier and arguing for a refund via ebay.
Lesson learnt (ouch)