it is the company's responsibility to provide PPE (personal protective equipment)
however, in my experience, knee pads probably won't help very much, after all you are still having to kneel on them, albeit a bit softer thn the floor, and are rather annoying for the in between times when you are not ctually on your knees 0Rther than pitting yourself against yoru employer, why not buy a cheap head torch (less than a fiver) and some knee pads (less than a fiver) and see if they make a difference first