Advice for new PC build

[Mywaterfall]

Hi, looking to upgrade my current PC I have at the moment.

Current PC build
GPU: GeForce GTS 450
CPU: AMD FX(tm)-4100 Quad Processor
Memory: 8.00GB RAM
HD: Seagate SSHD 2Tb
RES: 1920 x 1030 30Hz
OS: Win 10 Home

For new build
Budget - Up to about £800
Resolution - 1080p
Games - World of Warcraft mainly. Few Steam games.
Any other intensive software or special things you do (Frequent video encoding, 3D modeling, etc) - Thinking about streaming in the future, nothing else other than that.
Country - UK
Parts that can be reused - Seagate HDSSD 2TB
Do you need an OS? - Windows 10 (want to do a fresh start)
Do you need peripherals (e.g. monitor, mouse, keyboard, speakers, etc)? - Not at present. Currently using 2 x 22" Hitachi monitors, Razer Naga 2014.

Had been looking at this type of build - uk.pcpartpicker.com/list/XxpPxY (Sorry can't post link)

Only thing missing off list is the GPU as I'm not sure whether to wait till the 1060 comes out as did have the mind set on a Nvidia GTX 970. No case needed as will use my old one. Also would it be better trying to buy all the necessary parts from one place or just shop about? Also like to add I'm not too computer savvy at all.
Thanks

[Thunderball]

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6500 3.2GHz Quad-Core Processor (£186.98 @ Amazon UK)
Motherboard: Gigabyte G1.Sniper B7 ATX LGA1151 Motherboard (£70.33 @ Aria PC)
Memory: Corsair Vengeance LPX 16GB (2 x 8GB) DDR4-2133 Memory (£54.99 @ Ebuyer)
Storage: Sandisk X400 256GB 2.5" Solid State Drive (£63.25 @ Amazon UK)
Video Card: Sapphire Radeon RX 480 8GB Video Card (£219.99 @ Ebuyer)
Case: Phanteks Enthoo Pro M ATX Mid Tower Case (£59.83 @ CCL Computers)
Power Supply: EVGA SuperNOVA G2 550W 80+ Gold Certified Fully-Modular ATX Power Supply (£70.97 @ Amazon UK)
Operating System: Microsoft Windows 10 Home OEM 64-bit (£77.99 @ Ebuyer)
Total: £804.33
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-07-15 17:06 BST+0100

Add an optical drive if needed. You can save about £60 by getting Windows at Kinguin. Your build doesnt fit your budget unfortunately. If you have more budget I suggest, priority list: 1) Get a cheap tower cooler, like 212 EVO or PURE ROCK, whichever is cheaper; 2) Samsung EVO 850 SSD instead of this one; 3) Getting 6600K+Z170 Mobo if you need overclocking capability.

[chazus]

A bit confused on the Win10... You have it already. Why not just keep it? Why buy a new one?

[Mywaterfall]

A bit confused on the Win10... You have it already. Why not just keep it? Why buy a new one?

I had Win 7 then did the free Win 10 upgrade. I want to go a fresh reboot of HD and haven't got the product key to put it back on. Plus since I upgraded to Win 10 every time I start my PC up it go straight to the boot screen.