Obvious answer is apparantly not so obvious: Weld the mounts and clips back on... If you don't have them, obtain them from a scrapped clio.
Picturing the two brackets that hold the bench in place, it seems unlikely that you could attach them any other way as bolting them in would possible protrude in the outter skin of the fuel tank, and that's assuming the metal is thick enough to a tap a thread into. Apologies for useless post xD