Thinking about doing it, is it quite easy and what size of braid do i need for SATA and front panel wires?
It is dead easy mate. All you do is measure and cut your braid to size, leaving a few mm short at either end to allow for the heatshrink to grab the cable underneath. You might want to slightly melt the end of the braiding to stop it fraying.
Then push one end onto the cable and feed it along the cable by pushing the braiding from about 2-3" back off the cable. You will see it expand and slide along easily.
Then cut your heatshrink to the required size, fit it over the braid and use a heat source to shrink it, turning it regularly to stop it melting. I found a candle to be perfect for this. And that's it. Simple as that.
If you are planning on doing 3 pin fan cables, then it is best to remove the fan connector first. Google for pics of how to do this.
You would probably be best to buy a pack of heatshink and a couple of different sizes of braid so that you can do other cables too, as you will get the bug
At a guess I would say 8mm braiding is likely to do the SATA cables. But you might be better just to spend a couple of quid and buy black cables. That's what I did.
Just be careful what you buy as I bought a ready to go pack of heatshrink and braiding from another seller and the quality was rubbish.