How can I fit a ceiling mounted curtain pole inside a bay window?

I have a bay window and am trying to fit a B&Q bay window solutions kit (curtain pole) inside the recess. The pole goes through brackets which are ceiling mounted. I got the centre bracket up without any problems. The problem I have is that there are two side brackets for each end of the curtain pole. Underneath the plasterboard at each end of the bay there seems to be steel plates. I've tried drilling through the plates with a 3.5mm drill. Although I can get a screw through the plates this way, there is no grip to the screw and it's loose within the hole, providing no support for the bracket. I can't fit the brackets further along the pole as this would stop the curtains from opening and closing. I can't fit them to the wall outside of the recess because the steel plate seems to extend about 30cm down the wall there too. There HAS to be a solution to this somehow. Can anyone help please? Having spent all week making the curtains to hang there, I'm getting a tad frustrated now!