Trafic interior light cluster

hi guys I just recently fitted a reversing camera in to the van, after snooping on the site I took the 12v feed for the display unit off the interior light assembly. All works Greta however I cannot for the life of me get the housing back on. As I try and push it in the head liner just flexes and I can't get the clips to engage, any pointers will save my hair going grey.

Thanks