we got the system from a place in tottenham court road London, known for its discount electronics - we have saved hundreds there over the years where the shops try and undercut each other. we haggled and got an extra 50 squid off. We paid 1,200 including the disc changer. Not too bad for what it is me thinks.
We also fitted it ourselves after getting a quote for 350 to do it. It took all day cause we were ultra careful with the trim etc. Get some quotes or drive down to Kent and ill do it for 50!