There are amazing 3D ultasounds available now. We looked into it with Siobhan but by the time we found one she was a bit too old as we would be meeting her within a month anyway.
You have to go private for them and they aren't cheap but the results are amazing.
They even do video of the baby moving. Check out some of the example clips.
Here is an example company, there is one in Leeds I can't just remember the name of, Julie will be along tonight as I'm sure she remembers it
http://www.proscan-uk.com/11-gallery.htm