If you want Volvo, look at these:
https://www.ebay.co.uk/itm/Volvo-S80...72.m2748.l2649
https://www.ebay.co.uk/itm/Volvo-S80...72.m2748.l2649
Given that my original discs have lasted 100k front and rear, I reckon that is good value.
Their other service kits etc look good value too.