Vectra B Aftermarket Stereo

I have an X Reg Vectra B ( I think its a B) that has a CCR 600.

I have looked around this and other sites and see conflicting advice on whether I need a conversion cable or not.

I am not bothered about the MID showing the radio Station track etc, just the time would be good enough.
Also the Steering wheel controls are more of an annoyance so wouldnt be bothered if I lost them.

So do I need a conversion cable or not?

Thanks