Arctic Freezer 34 eSports Duo, solid cooler. As for the case, you can do better, get the Fractal Design Define Mini C if you want a plain black box, superb build quality with excellent airflow, and stick some Arctic P14 / P12 fans in the front, or if you want something even cheaper that still has excellent build quality and decent airflow, the Thermaltake Versa H18 is a solid case for £40 (high quality chassis)
Fractal Design Define Mini C:
https://www.scan.co.uk/products/frac...icroatx-mini-i
Thermaltake Versa H18:
https://www.scan.co.uk/products/ther...-2x-usb-20-usb
Both are mATX, to suit the MSI MAG B550M Mortar.