isar HE30 no display on user control?

The display on our isar he30 user control is blank. The heating and hot water still works so I'm not so sure its a problem with the pcb (but what do I know!). We have a remote programmer/timer which we can still use to turn on heating etc. I checked the manual and can't find anything about the user control. Whats the best course of action? Does it mean the system likely to break down soon? Any suggestions please?