Sorry for not responding sooner - there's so much great advice here.
However your comments have made me realise that my original sketch was incomplete. There is another window at the end of the room, above the sink, which means we can't have anything tall there (as an aside, we did consider losing one of the windows, but after an experiment with some temporary blackout blinds we've decided to prioritise light over storage space!). The doorway is actually a new one so I can ask the builder if the door can open out rather than in, which should make the fridge access a bit easier (the space for the fridge is actually 700mm - I'd built in some room for the door to open and drawers to come out).
I've updated to plan to show the windows, and take on board some of the comments. I've also got a kitchen designer coming over at the weekend, but in the meantime...
CountMagnus Re the dishwasher. We've got two young children and entertain fairly regularly. I'd like to think we could get away with a smaller dishwasher but most of the reviews I've read talk about them being best for couples. Maybe I need to reconsider.
PickAChew You've reassured me about stacking the hob and oven, and your point about carrying pans of boiling water is a really good one. I'm not having a bottle rack - I never keep them long enough to have any on display...
MrsMoasty The opening space into the dining room is only a couple of metres so I don't think there's room for a breakfast bar.
Everyone has picked up on the fridge being a long way away from the sink, but I think the only way to address this would be having separate under-counter fridge and freezer, which I'm not that keen on. Does anyone have this? I suppose it would mean I could use the current fridge space for a large larder cupboard or eye-level oven...
mrsmortis I was going to have an integrated draw in one of the pan drawers for utensils. You're right about oil, etc, though.
namechangedtoday15 I do think an integrated fridge freezer would be better (although it would have to stay in the current position - it won't go to the right because of the windowunder the sink). You've made reassess the wall units too. I'm not keen on them either but I've been working on the basis that we need as much space as possible. I do think they look a bit awkward, so I've taken them off the updated plan, but I need to work out exactly what will go in each cupboard and see if we've got enough room.