You have probably already discovered that there are quite a few place offering 0-DS courses. Depending on your sailing experience you may need to take the 14 day including CC, as already mentioned.
You may be able to take the theory portion online before hand which, if you don't have any real experience with meteorology and
navigation, will probably be helpful unless you are a fast learner. RYA schools typically offer this through Skippers Online. You'll receive study materials by mail consisting of a text, a book of practical exercises, and a couple of
charts of the fictional sailing area used by RYA during teaching. Remember, use VICTORIA for your tidal calculations. This will make sense once you take the course. Depending on the course you register for a
Portland Plotter may be included in the study materials. If not, buy one because it is the easiest way to learn what they teach. I'm not saying it is the best tool, it is just how they teach and as a beginner you should be able to achieve competence with it fairly easily.
Speaking of tidal, RYA no longer distinguishes between tidal and non-tidal
certification, however, I think it is well worth it to go somewhere with tides so you can experience them as you learn. I did and it was very helpful.
Finally, if you are going this
route you may want to consider adding an additional 2 day Powerboat 2 course to your curriculum. This will give you a well rounded intro to sail and
power, and set you up for
crewing on either a
power or
sail boat.
I hesitate to recommend a particular school/training centre because my experience with RYA overall has been good so I think you should choose based on what is most convenient for you and where you would most like to go to learn.