Check out the Dulux Mouse Painter - you can select the room and the colours you want to get an idea of what it would look like. Don't forget to get sample pots to see what the colour is like in your hall - with your lighting - natural and other!
If you get the chance you could go into a paint shop and look at the Farrow and Ball paint swatches. They also have a great book, which shows you the colours used in different situations. I really love their blue-grey for a hall, it really looks sophisticated if you have white with it. It gave me some great ideas and now I just have to find the same colours in a cheaper brand.