Weve had a multifuel burning stove for a couple of years and its been brilliant. However, even though we have cleaned the glass every day it has become discoloured and needs replacing. I have already acquired the glass/ However I had trouble loosening the screws that hold the glass clips in place. in the end I used my mole grips to loosen the screws, one or two of them, the heads have become scuffed by my mole grips. What kind of screws do i need? Are they just steel screws or do I need a specific type? Thanks in advance guys, any he,lp with this will be very much appreciated