I presume you have the Rally Nomad series caravan, the bumper is held on to the body with two screws concealed under
plastic covers at the corner. The other end is held on by velcro it needs a good tug to pull it free.
Repairing the panel depending where it's cracked could be tricky if it can only glued on the edges I think you will
problems making a satisfactory repair. If you can glue support plates at the back of the bumper much better.
Replacment parts can be ordered from Richard Olphin at Towtal (Stoke on Trent) He will need your chassis number.
If you decide to replace rathe than repair you will need both bumper panel and decals.