I clearly made a mistake that I won't repeat again, lesson learned.
I purchase the bundle together with Bryan Ferry's Blu-ray. 12 pounds total shipping costs for the three. So far, so good.
As I had no interest at all on INXS, I made the error of asking for the cancellation straight away. This meant Retrospective order was kept and the bundle cancelled, so I ended up paying another 12 pounds when I reordered Avalon.
Of course SDE support could not keep a single shipment as Retrospective was sold out..
Anyway, someone needs to feed Royal Mail, I guess.