Thank you very much!
There's still houses being built on the street, I've had a look and it's a masonry interior. From the look of that photo (and the feel when I knock on the part of the wall where I'd be drilling) it's brick behind the plasterboard. I'm assuming a drill with a masonry bit...
I've just moved into a brand new build house (it was finished in Feb 2015) and need to put up some curtain poles (I'm planning on putting them as close to the ceiling as possible, in order to help the ceilings seem higher) but I have no idea what the lintel is made of, or how to find out! Can...