I bought a replacement door handle for my front PVC door from B & Q. The handle fits ok except the screws it came with are not long enough. I can't find longer screws anywhere. I tried the screws from the old handle as well but they are too small in diameter. They are about 4.75 diameter and need to be about 85mm long, they have a flat end and a pan-head. Does anyone know where I can get these from? I have tried Wickes, B & Q screwfix to no avail.