Don't think it's available as an O2 PAYG, just contract (according to their site)

You could get a SIM free one (unlocked for all networks)
http://www.phones2udirect.co.uk/Prod.../NetworkID/280

http://www.mphone.co.uk/acatalog/6600_sim_free.html

http://audiovisual.kelkoo.co.uk/b/a/...3/9164513.html

It's about £130-150 on Orange PAYG.....