Here how to do it. Remove the light and turn over. Remove the backing foam from the light. empty your oven (electric not gas) and pre heat to a low temperature (warm not hot, your not roasting a chicken lol). Put the light with the cracked lens in for a few secs (remove torque screws on the rear because if you mess the light up, you have the chance to remove led unit and repair the original light). The glue will become soft and with a blunt thin object lightly pry the lense away. To reapply the lens heat the light and the glue will take to the new lens.
If all that seems long then pop down the dealers and pay £250+ Vat for a new unit
