Item delivered doesn't match item advertised.

[Shufflebumnessie]

I was wondering if anyone has any advice please.
I've just bought a bathroom cabinet as we're on the process of having a new bathroom fitted.
On the first attempt the company delivered the completely wrong item - a tap!
When the cabinet finally arrived, on the outside it looks the same as what we ordered but inside the one we ordered had:
3 glass shelves, the one delivered has only 2 shelves.
A mirror on the inside of the door, the one delivered doesn't have any internal mirror.

In the grand scheme of things it's not huge but it's annoying me that the item delivered doesn't exactly match the item advertised and ordered.

It wasn't cheap and customer services are being rubbish. Apparently the design has been changed but the website (& the one we looked at in-store) hasn't been updated to reflect the changes. We've been offered the display one from the showroom but they won't offer a discount on it. I don't want to accept one that I've no idea what condition it's in.

Does anyone know where I stand?
I would return it but a) it's the only one we found that we really liked and b) it's being fitted next week (needs hooking up to the electrics) so don't have time to order a new one.

Sorry for rambling on, I'm just feeling a bit frustrated.