There appears to be a single Bannan family in Andreas (Thomas bannan + Cath Christian)with children from c. 1795 to 1813 - Robert appers to be youngest son; the next son up Daniel appears as village butcher at Sandygate Jurby in 1863 directory
As far as I can tell the name does not appear in Andreas before 1795 (tho there is a good history of Andreas Families in Manx Museum) - the name is I think Irish

The first entry in IGI for Island is in 1783 in Rushen (a marriage) and then another marriage in German