I know it’s not a glamorous vehicle and it will never set anyone’s pulse racing, but I quite like my Vauxhall Astra. For a start, it has an engine, four wheels and a roof, all of which appear to be of adequate construction, and that’s always been a key consideration for me as a discerning car-shopper with absolutely no knowledge or interest in cars whatsoever. However, the one component that lets it down, as with so many popular makes, is the factory-fitted stereo.

The standard CD30 unit is competent enough, sounding OK if not outstanding and with the minor advantage of steering wheel controls. But it lacks one tiny, crucial feature that is more or less de rigeur for any car stereo unit today: a 3.5mm auxiliary jack so you can plug your phone in. (Also, there’s a weird 5 inch slot in it that appears to have no discernable purpose, and if you press the button marked ‘AM/FM’ then some lunatic starts gibbering at you.)

Fortunately, Vauxhall have made it easy to swap the CD30 for another off-the-shelf, aftermarket head unit, by making it a standard size and supplying a widely-compatible ISO connection. Like hell they have.

The CD30, despite its decidedly average specs, is larger than a 2-DIN unit, so you’ll need a fascia adapter plate to slot in a standard 1 or 2 DIN unit. Moreover, modern Vauxhalls use the CAN-Bus system for the car electrics which, from what I can gather, is effectively a computerised backplane for the entire vehicle. One of the consequences of this is that you can’t just get a standard ISO adapter for the Vauxhall quadlock connector behind the head unit, as the normal input connections are not present (for example, there’s no switched 12v feed from the ignition - instead, the CAN-Bus sends a signal to the stereo to power up when the key is turned).

Here’s the parts list I needed for swapping the CD30 in my Astra ‘08 reg (type H in Vauxhall’s nomenclature):

• JVC KD-X250BT Mech-Less Bluetooth Media Reciever: this is one of the newer head units that doesn’t include a CD player. It’s also compatible with both Apple and Android mobile devices, via USB or Bluetooth, and it supports remote control from the vehicle.
  The KD-X250 also includes a phone mic, which is connected via the rear of the unit via a long cable; running this around the back of the dash to emerge somewhere useful is outside the scope of this post (i.e. nope, I couldn’t do it).
• Fascia adapter plate, either 1 or 2 DIN to fit your head unit. You’ll need to check your dashboard colour to ensure it matches the finish; note that “chrome” and “satinstone” are close but not (quite) the same thing.
• Connects2 CTCVX002 CAN-Bus Interface Adapter: this supplies the ISO connector that interfaces the head unit to the Vauxhall Quadlock plug, plus the electronics for the remote control on the steering wheel and a number of optional features (parking sensor, illumination, speed sensor, etc.).
  Alternatively, you can buy a PC2-85-4 Fakra harness adapter, but note that you will need to take a 12v ignition feed from elsewhere in the car (the connector has a red fly lead for this). The standard recommendation is to splice the connection to the cigarette lighter socket with a fuse, which involves a minor amount of dashboard disassembly.
  My impression from reading the Astra forums is that the Connects2 lead, while more expensive, has better compatibility and less chance of electrical problems, and is certainly less hassle to use.
  Either lead should also include the required Fakra antenna adapter for the aerial connection, but confirm this.
• Connects2 JVC CTJVC3LEAD: this is the adapter for connecting the JVC head unit to the remote control interface on the lead above. You need the correct lead for the brand and model of your head unit. Note that, while this lead is usually stated as required for “JVC AVX” models, it’s also needed for the KD-X250 above and probably other recent JVC units; if your JVC radio has a single blue or blue/yellow fly lead on the connector, it probably needs this one.
• Removal keys for the CD30.

I was able to buy all of this apart from the head unit and JVC adapter as a complete kit from Dynamic Sounds (part no. CTKVX16).

N.B. If you remove the CD30 unit, you’ll also lose the ability to control the onboard computer display. The Connects2 adapter tries to compensate for this by allowing some basic adjustments via the left hand steering wheel controls.

The install procedure is fairly straightforward, but in outline:

1. Remove any CD from the existing unit and turn the ignition off!
2. Use the keys to withdraw the CD30 unit. Disconnect the Quadlock and aerial connectors (pinch-grip on the sides). Note that each CD30 is uniquely coded to the fitted vehicle so if you’re planning to resell it, you’ll need to get it decoded before deinstallation, using the appropriate Vauxhall diagnostic tool.
3. Remove the CD30 cage by disengaging the edges with a slot screwdriver.
4. Fit the fascia plate and pull the Quadlock and aerial cables through.
5. Slide the metal cage for your head unit into the slot (pulling the cables through again) and bend the various tabs to anchor it in place.
6. Attach the Connects2 adapters to the new head unit. The large interface block connects to the remote control adapter, and you’ll need to join the wire from that to the head unit connector block using some kind of robust joint (bullet plug, terminal block, etc.).
7. Connect the remaining ends to the Vauxhall Quadlock and antenna plugs.
8. At this point, with the head unit connected but not yet installed in the dash, it should be possible to test everything with the ignition on. Confirm that the unit powers up and that any tone and radio presets remain stored after the ignition is turned off. Also check the steering wheel controls (note that they’re now a bit sluggish compared to CD30 operation, probably because of the overhead in translating the signals).
9. Slide the new head unit into the cage. You’ll have a large bundle of cabling and adapters to accommodate behind the unit; there appears to be a small cubby hole to the upper left of the void behind the dash into which some of this should fit, which should help to clear space for the unit itself.
10. Attach any surround and test again.

The only outstanding wrinkle is that the radio will not operate at all without the ignition switched on; a minor inconvenience for having a more capable head unit available.