To factory reset your device the easiest method if you can access the stick or box menu settings is :-
Settings > System > Advanced System Settings > Factory Reset and enter the four digit code on your television screen then click OK.
If you can't use the remote controller and the screen is locked on the NowTV Stick hold in the small reset button on the stick for about 20 seconds, if using a NowTV Smart Box underneath the bottom of the box hold in the reset button for about 30 seconds, if using the older white or black box there will be a small reset hole on the back of the box and with a small pin push and hold the pin in the reset hole for about 30 seconds.
Please note with a factory reset you will have to setup the NowTV device once again from scratch.
Crikey...that was hard work. Did a factory reset and it appears to have done the trick (for now!) thanks for the guide peeps. If it goes off again I'm going to bring out me tin cans and string, quill pen and inkpot and wheel out the old CRT set from under the stairs. Now where's me cocoa? 😛