Your best bet is to do an RYA or RYA approved course for your Radio license, Day Skipper and Yacht Master.
Sailing a boat is easy it's all the other things that are important, Navigation, Meteorology, seamanship, Avoidance of Collisions at Sea Regs. and instant recognition of vessel lights at night
Getting the rules wrong in international and coastal waters can be VERY expensive, the fines are in the thousands.
Taking people onboard and getting it wrong with a loss of life can lead to a prison sentence for manslaughter. YOU are responsible for their souls.
It's amazing what you DON'T know and taking a vessel out without the knowledge is a very stupid thing to do.
Get your Yacht Masters, as I have, and you can earn money moving boats for owners.
I've spent many happy hours at sea navigating for inexperienced skippers and after spending a couple of days at sea arriving with in 10mins of ETA is sooooooooooooooooooo statisfying.
So to summarise RYA or RYA approved only in my mind.
Oh Yeh, then there's the boat handling Cert if you want to sail abroad.
HTH