Hi Tony, I have done this with D-I-Y Wills and the help of the Land Registry as suggested by Barmaid.
The following link will also help to get a pair of suitable Wills for £55 so no need to spend thousands.
http://www.tenminutew...home_page.cgi?page=51
Basically, You get a form from the Land Registry and make yourself and the wife to be "Tenants-in-Common" which means that you both own 50% of the property.
You then write Wills basically stating that if you die first, then your half of the property is left to the children (or whoever you wish) on the understanding that the partner can still live in the property as long as he/she wishes or as long as necessary with the balance of your estate being left to the partner.
So when you die, the kids get half the house, the wife gets your money and she can still live in the house.
When she dies, the kids inherit the other half of the house plus all the wife's estate.
There's plenty of "Will" info if you Google for it but you must be sure that the wording of the Will cannot be misunderstood or mis-interpreted in any way.