I have tested this and it works.
Download the App - works on all phones that will run an App.
You call the 08-- number and it connects you using you mobile phone contracted minutes, instead of charging you extra. However, it gets better. If you get stuck in a queue you hit 9*, and you are then disconnected, and the computer queues for you, calling you back when you get to the front of the queue. You don't pay anything for the reconnection.
It's a no brainer.