New but a bit old boy

[jonny round boy]

...like to learn how to fit kitchens properly as another skill.

Sorry, but you won't learn how to fit a kitchen properly on a kitchen fitting course.

If you want to learn, your best bet would be to find a fitter near you who you can work for/with, and learn the ropes that way. Kind of like an unofficial apprenticeship.

On the plus side though, if you can do plumbing & plastering, you're already part way there.