Alright, got it sorted. Seems the On Screen Reference REALLY is your friend...
QBFC already builds the properties when the RetList is populated. Nice... I was under the impression I had to iterate through a "list" of sub aggregates/nodes in the RetElement.
Using the following, works a charm.
RetListObject(withid).name.GetValue (etc)
'Sub Properties in Response
RetListObject(withid).ORSalesPurchase.SalesOrPurchase.Desc.GetValue
RetListObject(withid).ORSalesPurchase.SalesOrPurchase.ORPrice.Price.GetValue