How do I bathroom / kitchen / extension? etc.

That boxed-in corner thing looks quite a bit larger on the photo than in your plans. Might be significant if you're wanting to squeeze a lot of stuff in along that wall.

Personally, I would do the easy option first and live with it for a bit. Loads of things you think will piss you off in a house are actually fine once you get used to it.

If you like it then you'll save your self a load of money and hassle refitting a whole kitchen and if you don't it's a relatively inexpensive way to find out.

This. But swap the sink and hob.

Where are your zones going to be - cooking, cleaning, prep, other people.

You don't want too much overlap between those zones, as that's where people will walk into each other.

The last picture, the cook does their stuff free and clear of all the others in the kitchen (if you swap sink and hob, that is).

Maybe even swap oven and fridge.

In fact, do swap them.