There is no Inheritence Tax due when a spouse inherits - However, upon the death of the surviving spouse, any assets above the Inheritnce Tax threshhold will be liable.
This means your children (?) may have a large tax bill upon the death of the surviving spouse - especially with property prices as they are.
The 'Tenants in Common' approach means that each spouse has a separate share in the property / assets (usually half and half). Upon the first death, that spouse wills their share to someone other than their spouse (usually their children). The idea is that this half-share falls below the I.T. threshold, so no tax is due. Similarly, upon the death of the second spouse, the second half of the assets are passed to the children, again, below the I.T. threshold, avoiding the children inheriting the whole share in one go and being liable for Inheritence Tax.
There's quite a clear explanation
here.
The bit about 'do you trust your kids?' is a valid point, though !