I decided to have another attempt at a castle seeing as I was so displeased with my first attempt.
Using the align tool I managed to produce far better towers as the cones lined up perfectly with the cylinder towers. I also used the bevel tool to add extra detail. The door way also went much better by cutting out the mesh and adding half a tunnel object and a couple of cubes to add further detail as well as fill in the gaps.
Over all the castle turned out a lot better, I imagine my third attempt will really start to look great!