A halogen downlight bulb can easily be replaced by removing the base rim to free the old globe, or popping the entire fitting out of the ceiling, which tends to be easier as you are not standing on a ladder while fiddling with the bulb.
TIP: Turn the mains off and let the lights cool before touching them.
REMOVE THE LIGHT by switching off the mains for safety then pulling the light fitting from the ceiling. Hold the spring clips back to avoid being struck on the fingers then remove the plug from the bulb pins.
REPLACE THE GLOBE by twisting out the base rim that holds it. Discard the old bulb then position the new bulb in the metal clips and lock the rim back into the light fitting with a twist action.
REFIT THE LIGHT by reattaching the plug to the bulb pins. Force the spring clips back to a vertical position and slot the light fitting into the ceiling, allowing the clips to spring back. Turn the mains power back on.