Essex is a totally new county for me, I know nothing about it.

But I have an Essex born lad who married into my Burrow family so I would like to know bit more about him.

Name - Edward Bentall COLLIS
Born - 15 August 1885
FreeBMD - He was there under HALSTEAD for the Sept Qtr 1885. Also found a possible brother on freeBMD - John born Halstead 1883
At some point Edward emigrated to New Zealand. He married my grandmothers sister in New Zealand in 1924 and they had 2 sons.
I know Halstead is both a town and also a registration district.
Without the parents names I cant check the 1881 census. Freecen does not seem to have the 1891 census for Essex.
And I also cannot find Edward on the 1901 - not with a birthplace of Halstead anyway. He may already have emigrated by then.
My questions are as follows
Who were Edwards parents?
Was John his brother?
When were the parents married?
Were there any other siblings?
What village/town were they living in.
If anyone can indicate what (and where) online reecords there are currently available for Essex, I'd appreciate that as well.

Thank you
Burrow Digger