I don't know about in the UK, but here is what I did in the US. I went to lhe local Tax and Revenue office and applied for a business license. I am a Sole Proprietor and it is free for the first year. Then I went home and framed the license and put above my computer so I don't forget what I'm doing. Every year I go and renew it and the renewal fee is based on how much I made the previous year. As for fixing computers, you need some diagnostic tools and programs that you carry around with you. Whenever I fix a computer, if they bring it to me, I charge 1 rate, and if I make a house call I charge another. As for making flyers, Microsoft Word is a good tool. You can do all sorts of things to the text to make it stand out.