I sanded all the pieces, test fitted them together and discovered that they weren't perfectly straight so wouldn't fit together as tightly as I had hoped. This was especially important as I was just intending to glue the pieces together. So this time, rather than abandoning the project when I hit the first problem I decided that I would also use small nails to hold it all together as well as the glue. This meant that I could eliminate the need for corner clamps (I still hadn't found any to borrow anyway) as the nails should hold it together whilst the glue dries.
As the MDF I am using is only 1/4" thick, I was worried that just hammering in nails would split the wood, so I pre-drilled the holes using a pin vice and this is the result -
It's not perfect, but I'm really pleased how it's turned out. I haven't fixed the top permenantly yet so that I can access the inside more easily. Once I have completed the room box I will just glue the top on -
The next step is going to be constructing the fireplace. As the box has ended up slightly bigger than I expected I am going to include a false wall at the back so that the fireplace will look more realistic and have depth to it. New England Minatures have put a wonderful step by step tutorial together for doing this in their Kitschy Kitchen Part 1 Post. I am also going to be using their fab tutorial to create a flagstone floor.