With a SIM free price of £250, the Nokia 5800 should be available, via operators, for 'free', even on mid tier tariffs.
It is worth noting that a Comes with Music version of the 5800 will likely become available at a later date. Based on the cost of the N95 8GB and N96 'Comes with Music' editions, the 5800 'Comes with Music' edition will likely cost around £300. That's an impressive figure for a capable multimedia creation and consumption device that comes with a year of free music (and happens to be a phone too).
See Also
Nokia 5800 XpressMusic announced
Nokia 5800 XpressMusic Preview Part 1 - Hardware, Design and Touch
Nokia 5800 XpressMusic Preview Part 2 - Multimedia Capabilities
Nokia 5800 XpressMusic Preview Part 3 - PIM Applications, Application Compatibility and Conclusions