Hi I have a 2008 1.8 TDI Focus with the awful Visteon 6000CD sound system.
When it started to play up (randomly switching to 'phone mode') I decided to upgrade
So i fitted a BEAT290 CD Head Unit with SD Card Input http://www.online-caraudio.co.uk/shop/cd-mp3-head-units/beat-audio-head-units/beat-290-cd-sd-card-usb-head-1057470.html with a patch lead kit,
Initially alll was well
the audio system worked consistently and to quality was much improved.
But then I started to get problems with the alarm and central locking
1) all the locks clunking until the battery went flat
2) random alarm soundings
I refitted the horrid old Visteon and the locks and alarms are working properly again!