how to replace Zanussi grill element?

The grill element in my top oven (Zanussi) is held by two self tapping screws which tap into the top of the oven and are, according to the manual, 'removeable' to clean the top.
Both have FALLEN out and the holes are now too big to screw them back in. I can not get to it from above as it is a sealed unit - God Bless 'em.
Anyone, any ideas how to refix the grill element?