My old Vector had one, possibly the same. Went to station, parked with it over a kerb. Picked up 4 people + loads of luggage, reversed off kerb .... grrrr.
Anyway, I found it was made of pretty tough stuff, quite flexible. Back home, I pushed and shoved it into the shape it was before, which left just one big split from bottom to almost the top. There is a lip along the bottom, about 1 cm wide, so I got a bit of meccano and riveted it to the top of the lip to join up the 2 halves. You can only see the rivets if you lie on the ground under the front spoiler.
The whole thing was now reasonably sound. That just left the crack, so I got out my ersatz dremel (black-something brand) and made the crack a V shaped valley. Next, used a hot glue gun to fill the valley, next a quick trim with a sharp blade to level it off and a bit of touch up paint applied by brush.
Not perfect, but unless you come across someone who enjoys rolling around on the ground commenting on other people's chin spoilers, it will be un-noticed.
