Thanks for that Len, it looks pretty certain that you have found him. I really appreciate that.
I can't as yet find the 1851 census info that you noted but think I have found them in 1861 and 1871.
It is interesting that Robert's father is always referred to as Brannen even if the children are Brennan. Not quiet sure what that means.
Are you aware of anyway of finding out further info regrading their time in the Isle of Man. ie when arrived from Ireland, why, and when left for Liverpool and why?

Thanks once again it is really appreciated