I've finally got these pieces on the wall displayed in the way I wanted. All it took was filling the old holes on the wall then deciding that painting over them made the rest of the dining room look tired. Two hours later I'd repainted the room and I could set to work hanging. No easy task in my house - the walls are made of the hardest substance known to man. I used the hammer drill in the end to start the hole for the picture hook. I then proceeded to waste the rest of the day trying to hang them symmetrically. I finally realised that the frames were all a different size so no chance of a perfect hang. They were bought as a pack from Hobbycraft.
Lesson to self - you get what you pay for!