No problem, glad i can help .
The screws i used are the self-tapping screws which are commonly used for fans, but you can use any type you like as long as the fan is secure that's all that matters. I've seen some people use the butterfly nuts, but i preferr the self-tapping screw becasue they prevent any vibrations.
Also a thing to note when using the self-tapping screws when your screwing them into the plastic do it very slowly, i nearly cracked mines doing it too fast. Also when your drilling the holes for the screws, don't make them too big.
Heres a pic of the self-tapping screws, you've probably used them before...
Many many thanks, 1 last question I promise, the cutter size you showed in the picture, is that for a 120mm fan?
Removed the bottom bay this morning and tidied the cabbling up, the airflow is now a LOT better.