oh, and i have bad news. It does not work.
www2sms claims to send the sms and even reports that the sms has been successfully sent, no sms arrives (tested it by sending it to myself). Also if i login to my o2 account, I can see that i still have the same amount of free sms. So no sms has been sent. Sending an SMS via the o2 web interface works, though.

regards,
nexus