Bosch PCD612CGB /01 Gas Hob cover removal – burred screws

I have intermittent sparking from the hob and I want to replace the ignition device 422149 and, to do so, I believe that I need to remove the 4 burners each of whcih has two screws. Of the 8 screws (2 x 4) 4 have burred and wil not undo. They are made of soft-ish metal and using my tried and tested methods (cussing, gas blow torch, WD40 and mole wrench) have all failed miserably. DOES ANYONE KNOW PLEASE;

(1)
How can I remove these burred screws. Is there any tool I can buy, before I resort to drilling them out ?

(2)
Can I buy replacement screws here ?

Thanks
Kevin