You need to remove the 4 plastic securing tabs that hold the front grill in place then bend it forward.
This gives access to the sidelight chamber on the light units, remove the rubber cap then simply pull the lamp holder out.
Replace the bulb and refit (take care not to let go of the lamp holder as it will drop into the bottom of the headlamp unit...)
Put the grill back into place and press down the 4 lock tabs.
Richard Hulme, August 2015