Its not a huge issue, but we found some customers were getting confused and since the majority of our customer base is still in the U.S. right now we're trying to make things as clear as possible. In the ideal world, you'd be able to seamlessly send text messages anywhere in the world, but that's now how it works with Twilio... yet.
Important Note for non-UK Customers: if you would like to use a UK number for SMS please note that this is a domestic messaging product for sending messages to UK numbers only. Additionally, we are not able to guarantee delivery of international senders sending messages from non-UK phone numbers or from locaitons outside the UK.
This isn't something I've come across before - have I just ignored it from other services, or is this an issue unique to Twilio? Not that it will be of much importance I don't think.