UK backup LTE connection

I have just seen this. http://www.three.co.uk/Discover/Devices/Huawei/HomeFi?id=1299&aidset=1&memory=0&colour=Black It is a box which connects to the Three network and uses that as a broadband connection. There is a pay as you go option as well that would fit this need much better. It has support for external antennas, and I'm sure the WiFi functionality can be disabled. It has a 1g (yeah I know it will never reach that speed) you could connect to a PFsense box as a backup WAN.

I am definitely going to set this up, when I can get my PFsense machine. I know you could probably do something similar before, but this seems pretty easy and relatively cheap as long as you limit your usage while real broadband is down.