Back light to digital heating / aircon display not working

[Jag XFS]

Hi all I have just replaced my 3 ltr all wheel drive Jaguar estate for a 1.4 Yaris T spirit  and I am enjoying hi mpg £20 road Tax , I have an issue with the digital display which you can see clearly during the day but when it gets dark the back light is not working is this just a bulb I have remove the TomTom TNS410 stereo so I have access to the display , any help on this would be very much appreciated 

[Devon Aygo]

There is a setting to adjust the dash brightness when the headlights are on.

This setting only appears when the lights are on, using the press button up on the speedo display and cycle through the MPG, Range, trip info etc and you should also see a setting for brightness once on this screen press and hold the same button and the display will show and cycle through from bright > dimmer > dim and keep going until you release the button on your desired setting

[Jag XFS]

Hi Devon Aygo thanks very much I thought that it might be something like that but after looking for some kind of dimmer switch I gave up , you are a star thanks once again