I hadn’t thought about the testing the warning light bulbs so have been outside turning the ignition on and off.
With ignition on, the display in the bottom right hand corner comes up with the ABS, Battery and Handbrake warnings. After a second the ABS warning disapears.
Some way right of the handbrake warning should be the Brake warning – this light does not come on then the ignition is turned on.
I guess this could mean the bulb has failed, and wouldn’t tell me if there was a servo problem.