Advanced In Car Technologies
Why don't you go for something like this to put over the top?
Security Dummy Face Panel Cover for Double 2DIN 7" Car Radio Stereo DVD Player | eBay
It's not bomb proof but at least you keep the unit you want...
You're not going to get something quality for £300.
Tim - Project & Marketing Manager of Advanced In-Car Technologies LTD. An Audi Approved OEM / Retrofit Specialist Company. All views expressed are my own and bear no reflection on Advanced In Car Tech.