If you’re in the UK (Or Europe) then I recommended overclockers.co.uk. That’s where I’ll get my parts now.
Something to consider when building your own PC is to do research on noise pollution of your graphics card or the cooler for your processor. You could pay a lot of money for great graphics performance but when the card fans start spinning your PC might sound like a small jet engine is about to take off!
My desktop case has soundproof material inside to reduce such noise