Sloping gardens

We bought a house with a small kitchen with a two windows, a back door, an entrance hall door and a door into the backroom/dining room. We blocked up the hall door but widened the door into the back room and put double glass doors in that let in light so we could also block up one of the windows. We did have to walk from the dining room into the kitchen, but in reality it was only another 2-3m, but it gave a lot more room for units & worktops.
Or how about making the back room a kitchen/diner and the current kitchen as a utility so the kitchen doesn't have to have the washing machine clutter, etc?
Very annoying not having a floorplan to work to - this is the first thing we'd look at when house hunting!
The garden looks great and as if there might be gardening neighbours, too!
As an aside, check the upstairs extension really carefully for damp - I know you said it was fine - and also for insulation levels. We had a room like that, with a garage, rather than a space underneath, and it was bitterly cold in the winter having so mny external walls. It was pretty unusable without spending a fortune on additional heating.