You've got the right surname to help. I never thought about Hadden(in) as being a derivative of Haldon, Halden, Haldane, etc. I believe that the origin of the surname means "half dane" - ie, possibly Viking? Any idea?
Thanks for the info. Unfortunately John Haldon (1798-1840) died before any census. The John Halden baptised in Glenisa, Angus - possibly looks the most promising. Colmonell looks on map to be more away from coast and also Edinburgh (ie, Leith)? I'll check the Glenisa Parish Register to see whether he remains a candidate (eg, not died or married with children in the Glenisa area) - Can this be verified online?
Are the "Old Parish Register for Scotland" a reliable or complete source for Scottish BDMs?- ie, are all the known parish regsiters included?Thanks again