Looking at Graham's ladder-on-the-rudder there is one concern I would have. I had thought of fitting my ladder right in the middle, where it would project down over the rudder quite well. But if the rudder blade was tilted up, the ladder couldn't be deployed. Touch wood, I haven't fallen in yet, but the nearest I came to it was at anchor, when the rudder was tilted up. Similarly when I leave her on her mooring, the rudder blade is up, and getting into the dinghy is the time you are most likely to fall in and need a ladder to get out again. I always leave the ladder hanging over the stern when I moor her.
I hate to say it Tony and Johan, but one reason I didn't consider a CBL when I wanted a cabin boat was because I wanted a transom for a boarding ladder. Is it not possible to bolt on a ladder on one side just in front of the stern post? Or have a flip over telescopic one there, which could lie across the stern deck when not in use?