This packing is 600mm wide

Depends on the size if the kitchen and if you like to see lots of lines. Larger tiles can be used in a small room as they give the perception of size. You could go 500 x 500 or 450 x 450.

My general instinct would be to work with low level and indirect lighting, ie. table lamps and floor lamps, ideally all on a dimmer. Large statement lights work great in large rooms but since this is on the smaller side I would accentuate the cosiness. A large pendant can still look great but may just not be practical in terms of sight lines. Do you have photos of the room?

Concealed cisterns come in a range of heights, typically in the range 80-110cm. The shorter ones are obviously necessary if you want to box in to the height of an adjacent sink. But what are the advantages of the taller ones? Is is purely that they can be made shallower and still hold the same amount of water? Or do the provide a better flush because of the higher pressure? If height wasn't an issue how would you choose? Articles about choosing one all seem to concentrate on the aesthetics not the practicalities.