This GU new style genuine gearbox
Operation: Split spindle.
Latch reversal: Depending on date of manufacture either: Undo screw or screws in the latch, remove, reverse and reinsert; or push a flat bladed screwdriver into the small rectangular slot above spindle and pull out latch at same time. Reverse and reinsert.
Nightlatch reversal: Remove the latch to reveal a small screw. Use a small bladed screwdriver to turn the screw 180 degrees then return latch to the correct position.