Just been looking again at the 1814 Peel census. Wm Barr has two daughters (that's AFTER the death you refer to). If, as you say, Wm and his family then disappear, could these two sisters be the Mary and Ann Barr I'm looking for? I realise we have no proof, but I'm wondering if there's anything to disprove this? Mary was married in 1821 in Liverpool, though I am having trouble finding a William Barr of the right age in the Liverpool area. Just a thought?