I built my own - we live quite close and every night I would buy a couple of units and fit them together. Within two weeks we had a kitchen! That way I didn't have a huge delivery and stuff getting in the way.
If you are fitting your kitchen along one straight wall it's easy to do. If there is an L-shape involved it gets more complicated. Island units, therefore, are a piece of cake.
Don't use any kind of kitchen advisor - they are mostly men and have never cooked for a family in their lives. They really haven't a clue. We tried 4 different companies and they really didn't get the point of any of our needs.
Think about how you cook now, how you would like to cook in future, and take it from there. What is the busiest area, who needs access, etc. We have no wall cabinets so dcs can reach everything, also makes it feel more spacious. The kitchen triangle is a big myth. In a family setting you need a kind of kitchen octagon, where several people can skirt round each other comfortably. So we stuck our cooker out of the way, and have a special tea-making area. The dishwasher is near where the crockery goes. The larder is out of the way as it's not accessed often, the fridge is also tucked away slightly as you tend to get several things out at once. The sink is definitely not under the window but it is next to the dishwasher. Oven is under the hob. Using the space under the hob for drawers is not useful as you are standing there most of the time. Having an eye level oven just means it's more likely that if you drop your casserole it will seriously damage you as opposed to just making a bit of a mess.
I got quite bolshy about my kitchen, my inspiration came from the US - Americans seem to have kitchens exactly as they want them, they don't have any convention at all. The IKEAFANS website was very useful.
If you get larder cabinets, use shallow ones, 39cm deep. Easy to access and find what you want. Also, much cheaper. We have a wall of those for all my gizmos, vases, plates, store food, cat food etc etc. You'd hardly notice it's there as the cupboards are all the same size and plain white.
Enjoy!