Hi all,
There’s an incident affecting national & international calls for all MVNOs on our network, and possibly SMS and data while roaming in certain countries. We don’t yet know the cause; BT and our supplier Transatel are working to resolve it.
Data and SMS in the UK are not affected.
We’ll keep you posted with further updates,
Nick
This has been fixed as of 9:50 BST; I’ll come back later with a breakdown of what happened when we know more. 
Okay that is an excellent company name for a supplier. 
Hello, we have a few more details on what happened and when:
The incident officially started at 04:52 and ended at 09:56 BST on June 17th. 1 of 4 voice signalling components started flooding with errors; disconnecting, restarting & reconnecting it didn’t work, but everything went back to normal when the remaining 3 components were restarted as well.
They’re still looking for the root cause and why the first component affected the other 3. The emails we get contain a table of information, so we’ll set it up to automatically update the app with that info and a status page as well (we don’t have a timeline for this yet).
I’d heard tale of problems that couldn’t be solved in this manner. 
Didn’t think I’d live to see it myself.