How to remove the hob plate on New World Free-standing gas cooker?

How do you remove the hob plate on a New World free-standing gas cooker. I have removed the four plastic screws at the sides, but it is still firmly fixed. How do you remove the control knobs. Do they just pull off? I ask because my model 44440155 they seem as if they are very firmly attached and I do not want attempt to pull them off in case I break something.