Isis, I wouldn't stress too much about space, my quilting and cutting is all done on two wooden TV trays. I have them side by side in my bedroom, one is covered with a towel for ironing. I just shift things around as I need to, put my big cutting board on there when I need to cut, put that away and use the towel when I need to iron. Sometimes I will even put the sewing machine towards the back of the table with the towel on it, and use the space in front to iron small pieces as I go! It's actually a great set up in a very small space.
As far as designing goes, I find plain old paper and pencil and crayons work great. I have also recently started using excel by resizing the columns and rows and coloring them in to do simple designs.
Happy Quilting!!
Rachel