Half of those components in your build don't show as available in the UK:? How are you factoring in pricing?
While there's an additional 2 cores/4 threads between the R5 1600 and the R7 1700, the 1600 should be very capable for what you want to do.
Additional cores/threads will also be beneficial in editing though, so the R7 is definitely not a "bad" idea by any means.
***It's a balancing act, to accommodate the R7, you'd likely have to either increase the budget, or make sacrifices elsewhere.
For video editing, a GTX 1060 or 1070 would be more than enough, but within the budget, the raw horsepower gains with a 1080 would be a gaming beast. If this is strictly video editing, I'd take the R7 + lower GPU. If you want it to get the best of both, I'd opt for the R5 + 1080.
FWIW, the H75 (and H80i you originally used) are very 'budget' AIOs. Unless you're going for a quality, higher priced 240+mm AIO, I'd stick to air cooling.
The Noctua NH-D15 is a huge air cooler, but rivals most mid-high end AIOs. Something like the Cryorig H7 should be sufficient for moderate overclocks though.