1. Don't wait. Get planning permission and engage a builder asap.
2. A kitchen is for life and its contents will have to last for many years. Don't cock it up. Most likely you are your own Project Manager, ensure you have an easy time.
3. If you can find a builder that is good, considerate. careful, neat, helpful etc and will get the job done to your expectations or even exceed your expectations love him, cherish him and pay him.
4. Believe me the last thing you need is a bad or inconsiderate builder.