I've just had a vampire attack led by a couple of Master Vampires. I can defeat them relatively easy, but no matter what they come back to life as soon as I touch them. They seem to be virtually invulnerable to being fully killed. As soon as I touch them it says that I've disturbed its sleep before it lifts up off the ground, fully revitalised and starts attacking once again. Any idea how to permanently kill these bar stewards?

That's from a mod called Clean up your Corpses http://www.nexusmods.com/skyrim/mods/59340/?

You can turn off the feature through an MCM menu if you have skyUI

Really? I remember getting the mod, but I had no idea that sleeping vampires was a part of it! I got it mainly so I could bury and dispose of mortals more realistically.