What are you going to install into your Holden Astra (BL) Sedan
(we need this information to establish the correct parts needed)?

Unlike its Hatchback sibling, the Holden Astra Sedan (code BL) was not based on the European Opel / Vauxhall Astra and was actually based on the GM Korea Chevrolet Cruze with new bumpers and lights to look more like the hatchback.

The radios on the two cars are different, and require different parts to fit. See below for a picture of the "Mylink" radio fitted to the Astra BL Sedan.