Whatever you decide, DO NOT GET A GARMIN!
I bought one 18 months ago, and that sucker has more than once tried to get me to leave the A4 just before it becomes the M4 in London, when I was heading home to Cardiff. Heading into London once, it told me there was traffic ahead, and proceeded to take me on the most traffic-laden route I have ever tried to navigate, making me an hour late. And in France, I have been able to navigate better using the Force.
I can't remember the model number, but I'll post it when I can. Funny thing is, a friend was just making sarcastic comments about their own satnav, and it turned out to be the same as mine.
So that has to be scientific proof that they suck.