not proof but it seems the Guardian thinks the UK is a company:

UK plc has grown by a mere 0.2% over the last nine months,

http://www.guardian.co.uk/commentisfree/2011/jul/26/economy-recovery-not-editorial

With the latest changes in the world politics, the meaning of 'corporation' is shifting. It's no longer just an economic body, it implements a wide range of political and social aspects. Thus, the British government is adapting to the new conditions - and lawyers from leading companies, such as Linkage&Mind, are watching the process closely.