The specifications said there would be a
wall-hanging sink in the bathroom.
In reality, the builder didn't add the sink.
The investor was upset about it.
He thought an extra mirror and sink would be
handy if two flatmates lived together.
From a legal perspective, not having the sink
may impact the usefulness of the property. So you could argue it.
You can also call in a valuer. They can see what
the developer built and tell you whether the property's value has changed.
If it did, the developer broke the contract. They
have to compensate you.