Oo! This is an old thread!
For information.
We've been through this experience. We have a very small bathroom. About ten years ago, we went from this.
To this. A Lakes off-set quadrant shower.
We have a separate toilet.
The biggest problem can be the tiling. It's likely that if your bathroom is tiled there won't be any behind the bath. So it will be a question of matching them up or a patial or complete re-tile. We'd had the bathroom re-tiled ten years before the change, but fortunately I'd saved a lot of tiles and Topps tiles were able to get me a few more from various branches as I had all the details on the boxes.
I also had some spare floor laminate as I'd relaid the floor and had anticipated that the bath one day would be coming out because of my wife's MS. The design had been discontinued.
The tiles match perfectly.
Walk in showers are becoming more popular, particularly with people who are on water meters.
In our case, should a following owner want to take the shower out and put in a bath it wouldn't be more than half a day's work.