@23chris from memory if it's the Camec brand you push down on the top of the lens you will see two tabs.... Push down a bit more to pull the top out then slide the lens up to remove it to gain access to the globe.
If you have any issues doing it that way remove the 4 screws on the front and pull (Like tractor) to get the silastic/sikaflex to give way

and you can get to the globe from behind. Apply new silastic/sikaflex and refit the light unit!