I'd be happy to discuss this with you. My portfolio previously included museum services and I'm also a member of the Museums Libraries and Archives Council Board.
there's the Mutuals Information Service at http://www.mutuals.org.uk/ and Co-operative Public Services at http://www.publicservices.uk.coop/ which both offer support and guidance etc on doing this if people aren't aware of them (but as a Cabinet Office pilot I'm assuming you already are...)
you might also find this video clip of interest (although focussed on externalising mental health services still has lot of parallels) - http://www.youtube.com/watch?v=8AduAsnWMjE&feature=channel_vide...
I do a lot of work with 'spin-outs' from a range of different organisations. When I worked at University of Durham I actually led a spin-out and developed some insights into the processes. My background is as a Psychologist - so I am particularly interested in the personal, team and cultural challenges faced with such a change - this is usually a major barrier. Feel free to email me firstname.lastname@example.org