This is just personal preference Baz, but I would always go for as many "Velux" type rooflights as possible in a monopitch extension across the back of a house.
Roughly ten times as much light comes in from a rooflight as compared to a normal window.
I would certainly have no horizontal ceiling, but have the whole thing "vaulted". That is, plasterboard tacked up under the rafters directly. (Obviously loads of insulation as well.)
The effect can be stunning, and gives a feeling of a much larger space.
As for cupboards, my own kitchen is within a similar pointy space , although it's upstairs for the views. I have floor base kitchen units, and because of the slope, no wall cupboards at all. This is no problem because all the floor units are huge deep drawers.
None of that kneeling on the floor scrabbling around in cupboards full of junk. Everything is accessible by just standing over the drawers.
Sorry for such a long, rambling post, but I thought you might benefit from my experience. The whole thing's mightily subjective though.
I thought about calling mine "Marmite House". People either love it or hate it ;o)