I have a drippy kitchen mixer tap. Looks like the typical sort where usually I'd pop out the coloured dot, remove the holding screw then remove the handle/cap and then access the valve/whatever that part is that actually does the turning on/off of the water to the tap. However, the coloured plastic bit on the side (that covers the screw head) just will not come out. Anyone got any tips before I resort to destroying it entirely?