Can't read beyond the paywall but this has been in the news in a few places. Sounds a bit like von Neumann's 'astrochicken' idea, as elaborated by Freeman Dyson:
http://en.wikipedia.org/wiki/Astrochicken
Although I dunno if the Milner/Hawking idea is anything advanced as self-replicating automata, as von Neumann originally envisaged:
http://en.wikipedia.org/wiki/Self-re...ing_spacecraft
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