I am sure death in service benefits, like life insurance, pass directly to the named person, so never fall in to the estate of the deceased person, and so are not liable to Inheritance Tax. Your employer or pension provider should be able to confirm that.
And yes, I understand that when you die, anything over the Inheritance tax threshold (thinking about it, it may be nearer the 400/425k mark now) will be taxed at 40%. You can only pass to your spouse completely free from IT.
If you pass to your spouse, then he passes to your children, they only pay tax above your combined inheritance tax thresholds (so 2 x 425k = 850k).
If the property is held as joint tenants, the legal position is you both own all of the property, so if one dies, the other is left as the sole owner: you don't inherit the other person's share, so that is completely outside of the IT tax calculation, until the house passes to your children, when it will be liable to tax if the estate as a whole is worth more than 850k.
Am sure someone will shout if that is horribly out of date. Don't know about the benefits at all.