Allan,
Thank you, I would be very interested in your research. I have David details you stated, I noticed that he was the 2nd child named David, the first born 1780 and dying 1796. Trying to trace the Liverpool side is also quite tricky. I have a baptism date for David Cretney born 1825 Liverpool, son of David Beloved Cretney and Sarah. No other info follows through for David and Sarah but in 1842 I have David Cretney Widower marrying an Elizabeth Cain (I notice another manx name!) in Liverpool. Again father for this widowed David is David occ Sailor. David 1825 married in 1851 in Liverpool, occ Sailor father occ Sailor named David. So many David Cretneys...! The David Cretney born 1825 had several children one of whom was named Alexander married 1874 noted as minor so under 21 - father David occ Sailor. This Alexander Cretney was my gt grandmother's father.
Hope this makes sense.
Regards
Sue