Living off the grid might seem appealing to you at 19, but ironically in the UK you need some form of start up cash to enable you to live off the grid. Buying a plot of land or something similar, setting up the necessary technology and generally supplementing what you can realistically grow/farm with goods from shops... its all going to cost money.
I took the opposite route when I was your age. I decided that the way forward was to earn a lot of money while I was young, work hard at developing businesses that would pay off later on and for the most part I succeeded. Problem is life got in the way, so a brain tumour, separation from a long term partner and effectively starting again has given me a different perspective. So new perspective, earn lots of money while I was approaching middle age, work hard at developing businesses that would pay off later on and again, I had some success. Life got in the way again, but this time just me not being happy. Money is great, but it took me 20 odd years of adult life to learn it wasn't the be all and end all of existence.
Sounds to me like you're fed up with working for employers and being tied to the urban environment... so why not look for a middle ground? Why not meet people like Dave Budd... he's a blacksmith who works with traditional methods, but still makes use of modern technology. He lives in both the natural world and the urban environment, balancing the two. Hamish (Dreadhead) is a leatherworker who works with traditional methods, but still makes use of modern technology. He lives in both the natural world and the urban environment.
See what I'm getting at? You don't need to go full on man of the woods to live a different type of life to the nine to five, but the thing those two gents have in common is they're both incredibly talented craftsmen. They've learnt their trade, adapted their trade to the modern world to make it viable and they enjoy a mixed lifestyle that (hopefully) they both find fulfilling.
It is one way, not the only way, to achieving something different. I spent time on a course with Dave Budd almost exactly a year ago and it changed my perspective... and a brief encounter with Hamish has changed my life almost entirely. Sounds all dramatic, but in some ways it is.
Rather than leap into the unknown and try to do it all at once, why not take some baby steps, see whether there is a craft you like from leather working to blacksmithing to basket weaving? See if you can make a living from a traditional craft and move away from the employer/employee relationship and be more self sufficient financially. If that is a success, maybe then consider moving into a rural area, renting a place and making a living just from your craft. And if thats successful, maybe find a plot of land or a woodland somewhere that you can be the caretaker of, and use your craft to be self sufficient and live off the grid?
It's not running off into the wilds instantly and it will take some time, but time well spent now while you have youth, fitness and more importantly enthusiasm on your side will pay off in the long run.