Ray is quite right. It is usual for couples to own their homes as joint tenants, assuming you are both named on the title of the property (not in one person's name only).
It sounds convoluted but I will try to explain it. As joint tenants you do not each own a half share of the house. Effectively it is held in trust and the whole is owned by Joe Bloggs and Jane Bloggs as if Joe and Jane were a single unit. It is not possible for either Joe or Jane to sell one half, or leave a half share in a will to a third person.
Assume Joe has died. His name is now removed from the Joe and Jane Bloggs unit and Jane Bloggs continues to own the whole.
This means that the house cannot count as part of the �125,000 threshold.
With inheritance tax becoming an increasingly common threat more couples are severing their joint tenancy and owning their own homes as tenants in common. When Joe Bloggs dies, he leaves his half of the property to a third party (the children perhaps) and gives Jane a life interest so she can continue to live in the house. This has effectively disposed of half of the value of the house.
So when Jane dies, hopefully her half will still be under the inheritance tax threshold, and the children can inherit tax free.
It's explained much better here:
http://www.avoidinginheritancetax.com/avoiding _inheritance_tax.htm
And you didn't even ask about it. I'll shut up now. :)