I hear what you are all saying about extending, but a loft extension isn't a possibility, due to the shallow angle roof. We would have to go above the roof line (we are at the end of a terrace). Extending out the way would be possible, but the garden which is something that we need, would be severly cut down in size. It just wouldn't work.
As well as that, we are also moving for a better school. There is the option of placements etc, but nothing is guaranteed, and I've heard rumours of it getting harder.
A move it is, I'm afraid.