Think I payed no more than £180... altogether to fit it was £230 with me doing the work, due to adding an additional fusebox (not necessary, but if you plan to link more powered items in, it does make it a lot easier, like gauge).
Have a look on ebay, they have changed a lot since I bought one, they come with more features now days as models vary drastically for hardly much price difference... like they now have additional wires for reverse gear etc... Only thing I wouldn't bother with is fitting the TV kit, a real car aerial costs in the £100 and it goes under your roof liner.
It's just over 2 years since that's been fitted and no problems.