I bought the Road Angel Sat Nav. So it had the 'black spot' cameras and sat nav all in one. Excellent system. Cons to the system is that it doesnt download automatically but very easy to do via website. Doesnt pick up lasers.
Cost �249.00
i bought the tom tom 700 go for �299, works ok but struggles to find a gps signal at times and decides to start telling you which way to when you're well on your way. i've also just had to take it back to dixons after 3 months as it refuses to turn on. its directions (when working) are spot on though.
I'm currently looking at them, kindof, but one bit of advice is you may need an external ariel as some windscreens have a heat reflector and the GPS doesn't work too well behind it.
From what I can find, the high end TomTom ones aren't bad and the Garmin ones are nice, but blinking expensive. I think the top TomTom ones can actually give you live traffic reports too.
Oh just remember to remove it from the car when you stop or it'll get pinched.