As a starting point, it's always worth collating a visual mood board to get an idea of what you love. Play with layouts and get your tape measure out, work out what works best and what your requirements are.
'If you’re looking to change the space at all, or extend, you may need to find a local architect to help you realize the space and show what can be achieved within budget. Once you have the boundaries of the space, I’d then begin talking to your kitchen designer to start developing the design,' advises Fred Horlock.
Another thing to note is the timeline, if it's a big upheaval then you may need to consider moving out for the duration unless your current kitchen can be moved into another room temporarily.