Buying Windows 8?

I've decided to build a pc after coming to the conclusion that consoles just don't cut it.

But i'm confused on how to get an operating system and why windows 8 is soooo expensive (up to £100)

On the tek syndicate build videos there is no addition of the OS price and therefore makes me wonder if it comes free with the CPU/Motherboard/Any other hardware.

To add to this i'm not sure which version of windows 8 i should purchase and which is best for my needs.

Please help!!!!!

Grab the standard OEM version for around £70. Very few people require the pro version, it's orientated for business functions.

If you needed the pro version, you would know it already. Trust me.