Maybe check out:
http://metallicgear.com/products/Neo-Series-uATX-SR at 190mmx410mmx385mm. At £75 bit hefty for £700 budget but looks good quality. Black model also available.
The silver would go well with an MSI B450M Mortar Titanium. Black would go well with the normal MSI B450M Mortar. Buildzoid said if going with AM4 micro-ATX it's pretty much best choice compared to competing micro-ATX boards and that the mosfets are quality and heatsink is good.
Silver theme spec:
Ryzen 2600 - £146.50
MSI B450M Mortar Titanium - £95.18
G.Skill Trident Z 16GB 2x8GB DDR4 3200MHz Silver/White - £120
Western Digital Blue 3D NAND 500GB SSD - £53.99
Seasonic Focus Platinum 550W - £74.99
Metallic Gear Neo Micro Silver - £74.90
Gigabyte AMD Radeon RX 570 Gaming 4GB - £139.97
Total - £705.53
Black theme spec:
Ryzen 2600 - £146.50
MSI B450M Mortar - £88.97
Corsair Vengeance LPX 16GB 2 x 8GB DDR4 3200MHz Black - £112.34
Western Digital Blue 3D NAND 500GB SSD - £53.99
Seasonic Focus Platinum 550W - £74.99
Metallic Gear Neo Micro Black - £74.90
Gigabyte AMD Radeon RX 570 Gaming 4GB - £139.97
Total - £691.66
RX 570 4GB for 1080p 60Hz will be okay, especially if you plan on upgrading monitor and therefore GPU, next year.
Bit annoying that 3200 RAM is £20-30 more expensive than 3000, especially for a Ryzen spec. You could shave off some there if you don't regret not getting the 3200 for a bit extra performance.
That case could do with a couple of good value for money Arctic Cooling P12 120mm fans.