The RYA training scheme assumes you want to learn, so it has little need to restrict you. No limits on distance from shore — an RYA certificate records what you can do, not what you may not do. It does of course appeal to common sense: that you are aware of your limits and want to keep improving.
RYA instructors go through genuinely extensive training. Reaching that qualification is proof not only of a high standard of seamanship, but of a personality able and willing to pass on knowledge in a genuinely human, effective way. They also have to revalidate every 5 years, so what they teach is guaranteed to be current and technically correct.
RYA is also known for its emphasis on the quality of its training, and as the certification of a British maritime power it is accepted and recognised worldwide.