Those arn't the best prices tho TBF the £80 Biostar board is out of stock.
Z370 ITX and 6 core i5 for sub £290 you say? Let's hope so.
The £80 Biostar board is out of stock? I can't even get one any where in the UK since launch, and I was trying to since it was announced, and have checked pretty much every e-tailor in the UK. I ended up with the ASRock B350 version instead, which was £109 when I got it, and is quite awesome to be fair, especially with the included Intel WiFI & Bluetooth module, it OC's well too, had the RAM running at 3466 14/14/14/34, and R7 1700 at 3.925GHz with 1.2775v.
As for the processor yes, it is the best price, literally no where has it for less than £187 due to supply demand it's holding the price well.
EDIT: No sooner have I typed that, I just found the Biostar in stock somewhere! It's £116.16 + P&P for the B350GTN, so looks like it's not that well priced.