Title's a bit confusing, but when I fitted the mud flaps to the car, I removed the plastic insert that stits inside the wheel arch (theres probably a technical term for it) and mangaged to wreck one of the plastic threads that the screws screw into. The nut is like a small yellow'ish' plastic doughnut shape with a whole in the middle built into the bodywork...
Anyone got any ideas as to how to fix it or replace it... It doesn't look like you can take it out very easily....