We can sort you out for UK sms. Currently we have customisable billing methods (number of messages/periodic rebilling) setup for website access:
user sends sms -> we process it -> send them a password -> they use password to login to your site.
If you want to handle the autentication scripting yourself we can provide a simple HTTP based integration method. We also have some scripts that can be used / mod'ed.
email me
[email protected] / icq #41012160 if you want to chat about it.
Richard.