Any help appreciated, need to remove the heating element from a 18 year old Neff built-in oven as the grill is not working and only the bottom of the oven heats up. there appear to be 2 hexagonal screws, can't work out what to use, have tried some screwdrivers from halfords but no luck as they seem to require more of the screw showing they are quite flush to the back plate any ideas?