I a not sure about NI but this might be correct:
"The amounts shown below are for Northern Ireland deaths on or after 1 January 2008.
If the deceased was married or in a civil partnership
If the deceased had an estate worth £250,000 or less, then everything goes to the husband, wife or civil partner.
If the deceased had an estate worth over £250,000, then the husband, wife or civil partner won't automatically get everything. They will receive:
personal items, such as household articles and cars, but nothing used for business purposes
£250,000 free of tax (£450,000 if there are no children) and the interest thereon
if one child, one-half share of any residue remaining, or if more than one child, one-third share of any residue remaining
The rest of the estate will be shared by the following:
children (or if none, grandchildren) will get an equal share
if there are no children or grandchildren, surviving parents will get a share
if there are no children, grandchildren or surviving parents, any brothers and sisters will get a share (or their children if they died while the deceased was still alive)
if the deceased has none of the above, the husband, wife or registered civil partner will get everything."
I would do it yourself and not pay a solicitor nor pay them by a share of the estate unless you really feel you want to do so. I did my father's estate in England and it was not difficult.
Many life policies and work pensions etc are held in trust for the spouse because the employee has filled in a form to make that so. If that is done then in England at least they then are not subject to inheritance tax and are automatically the property of the spouse and to that extent regarded as falling outside the estate - same as joint bank accounts and houses held in joint names as "joint tenants".