I'd take a lot of time and research your options first.
Once you have some basic skills a course will provide, where are you going to get your work?
Advertising is expensive, you can't work on sites, you've no customers. It will be difficult to earn as much as you have now as a courier for a couple of years so how will you support your lifestyle?
There is a section on courses on the forum somewhere but as established Tilers we are not allowed in there as we are too negative towards newbies to our trade. To me it's just being realistic and if you have what it takes go for it because this is the best hobby in the world.