First off, you can make it of your good enough but it's hard work and you'll need a lot of patience. You get customers not being able to explain faults properly and wanting the earth, delivered within an hour for £20! Also, be prepared to learn and get frustrated. No matter how good you are sometimes things don't go to plan and even the simplest jobs turn into a nightmare - try spending 3 hours playing with a toilet cistern then get an air lock all for £15!
Finally if you feel you can put up with all that then apologise to Safe Gas, as I guarantee you could benefit from his advice and help at somepoint!
Sorry for the long post but if you take it on board and still want to be a plumber then good luck and welcome to the forums!