| I have a rather inconveniently laid out victorian terrace with the
| stairs in between the two rooms upstairs and down which means that
| you have to walk through the back bedroom to get to the bathroom -
| unless you halve the floor area by making a corridor around the edge
| - thus spoiling the better bedroom.
| http://uk.geocities.com/gentlegreeng...outchanges.JPG

Looking deeper into the problems of this small house, the existing stairs are unlikely to comply with current regs, so the proposed stairs to be compliant wouldn't fit. You may be able to get approval from the planning department without which you will come unstuck when you sell.

Have you considered a loft extension?