The Second Chronicles of Amber by Roger Zelazny are £2.99 at Amazon UK today:
https://www.amazon.co.uk/dp/B09S6GJ15K
This omnibus contains
Trumps of Doom,
Blood of Amber,
Sign of Chaos,
Knight of Shadows and
Prince of Chaos
The First Chronicles of Amber Omnibus also seems to be £2.99, but is marked as unavailable for some reason.
https://www.amazon.co.uk/gp/product/B09L5ZVLG1/
It contains
Nine Princes in Amber,
The Guns of Avalon,
Sign of the Unicorn,
The Hand of Oberon and
The Courts of Chaos