This assembly includes a plastics material structural frame (2) including at least a lower cross member (8) and vertical struts (10, 12), each of said struts (10, 12) forming, over at least a portion of its height, a deformable energy absorption component (14), the module further including a plastics material shield (4) formed so as to match the shape of a shield skin (56) and arranged against the structural frame (2), said shield (4) including an upper cross member (34) and a lower cross member (36) interconnected via vertical connecting beams (38). The upper (34) and lower (36) cross members and the connecting beams (38) include a plurality of ribs (48) which form cells (50) in the cross members (34, 36) and the beams (38), at least some of said cells (50) passing through the shield (4).