Your Plus 4 should have a single din blanking plate in the heater box. I would think, given the year, that like my 2011 it is radio prepped with speaker location holes behind the footwell carpets and speaker wires and power supply plugs also.
The system I have just bought to install is a Blaupunkt SQR46, pricey but classic looks with DAB, Bluetooth, USB & SD Ports.
John
