I want to learn how to repair and build computers from scratch, it’s something I’ve always wanted to be able to do. What I’d like to know is where do I get started with all this? Bearing in mind I’m a complete novice to this, where would you recommend I started? Thanks in advance.
The all-round guide to this kind of stuff I’d recommend is www.tomshardware.com , although it does go into some depth. Google will turn up plenty of websites about building computers, although these are often of dubious quality, and can be very out-of-date.
Your easiest route to building your first computer is to get hold of a motherboard bundle pre-assembled, which means the mots awkward task - fitting the CPU and heatsink - is done for you. Then it’s a basically a matter of choosing your graphics card, hard drive, case, etc, and bolting the pieces together. 
You have a wealth og information available to you on the internet. Try thissite too, OverClockers.com , check out the links and the how to section.
Director Kevin Smith’s sister told him that if he wanted to be a filmmaker he should just be a filmmaker. That is, just start doing everything the job requires. Don’t get permissions, etc.
So if you want to repair computers, repair them. Go to thrift stores and buy $10 junker computers. (Some only sell “good ones” but others have old models available for practically nothing.) Take them apart, they usually have a problem or two. Fix them. Learn what having a bad PS, HD, memory, looks like. A lot of problems are software/OS issues. Learn how to diagnose that stuff.
Out of date gear, but nothing to lose ripping them open.
Then start on newer gear. See a part you don’t recognize? Lots of web sites will tell you about them. Learn how to look up FCC ids online, track down manuals, etc.
Once you know about the new stuff, then it’s time for the Real Computer Geek test: Hot flashing a BIOS.
Note that repairing desktop PCs isn’t much of a business. Repairing laptops is definitely more profitable. Pretty much the same advice, but learn desktop repair first.