Nothing happens to mobile after sending confirmation code

Does your mobile phone number appear correctly at http://twitter.com/devices even after you've logged off and back on again? If not, press the Delete and start over? button (if it's visible!) to delete the incorrect number, and try again. For the UK, your number should begin +44... (i.e. in the form that someone from overseas would use when calling your number).

If so, everything is OK, and SMS text (other than Twitter commands) you send from your phone to Twitter should appear in your Twitter timeline at http://twitter.com/home.

That's all the response you'll get at the moment, I'm afraid. Even when your phone is correctly registered, you will only be able to send SMS to Twitter via +447624801423. You will never receive any SMS from Twitter via that number.

Click here for more about this, and for some alternative ways of receiving Twitter SMS text.

Twitter are working on restoring full SMS services to countries outside Canada, India and the USA, but negotiations are complex, and we're unlikely to hear much more until national deals have been finalised.

You should also note that Twitter's international number is based on the Isle of Man (which shares the +44 international code with the UK), and most British phone companies charge SMS to that number at high international rates - so take care! (Certain O2 contracts appear to be more generous, as reported by a couple of acquaintances on different O2 tariffs, though I don't know if this still applies).