Hi, Charlie, This looks like an interesting plan -- what are you doing about lighting for the work surfaces? Will you have under-cupboard lighting? I know you say you don't like downlights (recessed spots), however they can be extremely useful (on a separate circuit) to have as additional worktop lighting, to make sure you don't work in the dark! Their unobtrusiveness also allows you to have the style of light fittings elsewhere that you want, which might not be enough light on their own. Regarding the ceiling fittings; I do get that different ceiling heights are a challenge. It all depends on what you want to light, and if the lights as positioned will work for your lifestyle. However, I wouldn't worry too much, and instead make sure that all areas have enough light for their purpose. Depending on the fittings chosen, you could even have one large pendant rather than the two that are shown over the island (between the RSJs); although two smaller fittings would also work, as shown. What will that single, circled fitting light? It generally works best if the light fitting has a specific purpose and is lighting something in particular rather than just a patch of floor. Would it make sense to have it over the island at that point rather than between the island and cabinets? That could also be a track over that part of the island if that is what you like, as long at is is simple enough to work with whatever pendant fittings you choose for the other area. Or it could be a pendant matching the others, even with the different ceiling heights.

Hello R countryside, One way to view the idea of differing heights re the ceiling is to approach this from an entirely different angle... Rather than consider the heights of the ceilings and worry about them. Instead focus on the decor height of the internal walls.. Ie where you paint or paper up to. Or consider floor and walls together to create a feeling of space. Another way to create a seamless and coherent look within the extension is to decorate with the same palette throughout... It doesn't have to be magnolia... It could be any colour either dramatic or more muted.. Consider too the possibility that you keep the palette the same from walls to ceiling.. Several visual examples for you to look at for inspiration too to compliment what I am suggesting here. One of my favourites is to colour block, and this can be another way to add a dramatic decor that you can taper off to the desired height and keep above to a single colour or not... :)) A period property but you can clearly see how the colour can swiftly dictate an eye level, and above picture rail height the cornice and ceiling is treated as one. Of course you don't need skirting, dado, picture rails to paint these. It is an old but a favoured decorating technique, that is surprisingly versatile... Here I would have painted the skirting either the same or a shade up or down depending on the flooring.. So you can dictate how the eye sees the rooms by deciding the heights (ie the wall decor) so to speak.. Here's the same principle but at dado height... (for some reason they're all dark which I love but they can be a palette you love.. Or be bold with a colour and do everything one colour with a shade darker on the ceiling.. This will reduce the height. The same could be applied to 1 colour in entirety. Then you add interest and texture with everything else! Furniture, lighting, placement, collections.. the possibilities are endless... 1 colour need not be boring. It then relies on texture the air of intrigue in your furnishings and lighting.. Also consider the heights of lighting.. Pendants or clustered lighting can be low and offer a dramatic statement over a table or a side table for example. Or a favourite reading chair.... Steer clear from ceiling acne ( my term for spot lighting) instead look to floor lights, wall lighting which can have an upwards illumination but of a more diffused and interesting appearance overall... For a softer glow.. Colour blocking is really fantastic you can be creative and still continue a theme throughout... The variations are really endless and can be considered on the flooring as well for wood floors... :))

Do you have to have wall units on that wall? you could go for shelves and avoid the headache. Or maybe you could get a carpenter to box the gap:or build small fake units: Or use some slim cabinets:

Tall units up to the ceiling can look very nice, although would function as displays mostly. Honestly standard height kitchen wall units wouldn't concern me, they might accentuate the height which is not a bad thing at all. Alternatively if you have enough storage in the base units why not skip wall units altogether? Open shelves or even nothing, just a stunning splashback