Not being a arse, BUT
You do actually have rights as a consumer to ask for the other item / money back. Especially even more when buying items over the internet.
Theve failed to provide a service, i can point you to the right consumer act if you like? If mr.posty took it, its there problem not yours.
Let me know if u want it ! again sorry to be a arse but i know what id do in this situation!
PS. Ive brought stuff from BD before, all fine for me