Dear Bruce,
I am hedging that the rightful Elizabeth Corrin is as you first identified (John and Ann Preston). Henry does not surface until the 1841 British Census (Thanks to earlier help). Douglas and Arbory all come into play. A farm in Arbory is actually identified.
Henry is identified as 10 y/o then, which rings true if the US 1880 Census is correct (born IOM 1831).

Good tidings sir and thanks,
Dan