Music Magpie ebay look to have significantly reduced various PS4/Xbox One games pre-owned to £6.99 – worth a punt.
Some games below – probably more
Also try Amazon/Music Magpie listings if stock runs out as they seem to have the equivalent listings
Star Wars Battlefront 2 Xbox/PS4
Call of Duty: WWII Xbox/PS4
Wolfenstein II: The New Colossus Xbox
Monster Hunter World Xbox – thanks greyfox
Forza Motorsport 7 Xbox
Assassin’s Creed Origins Xbox/PS4
Call of Duty: Modern Warfare Remastered PS4/Xbox
Destiny 2 Xbox
Middle-earth: Shadow of War Xbox – thanks Threepwood
Tekken 7 Xbox – thanks zagroo
South Park: The Fractured But Whole PS4 – thanks JusticeUK
Middle Earth Shadow of War Xbox