Cannon.../Egan

Hi,
I'm trying locate information on William Cannon born 1815/16, son of Thomas Cannon and Matilda Graham.
The paper work I have says he born in Bangor, King's County...
As there is not a Bangor in Offaly we figured it was a misprint and was meant to be Banagher.
Thomas is listed as a blacksmith.
Again dates are a little sketchy and family mythology was very wrong.
William has arrived in Australia by or in 1846.
At this time he is working along side James Egan of Tullamore, King's County.
In 1852 William marries James' daughter Margaret in Melbourne, Vic.

Primarily I'm looking for the elusive Cannon's but all information is good.
And assistance would be greatly appreciated.