i pulled my out of shape rear bumber off the other day, got a block of 2by4 and a large hammer and beat the boot tray/wall back into shape. (it was all pushed in, the spare tyre wouldn't fit)
the licence plate holder was pretty much flat, gave that some rough love and its all come right. hit the bumper with some white spray paint and its sorted.
ill get a new bumper one day, but i'm fine with it.. certainly looks a lot better than it did.