I think the Garmin StreetPilot c320 is excellent value for money. It is an easy to use Sat Nav, cheap to buy and has complete coverage of Europe. It comes with clear instructions and can easily be removed from your car for security.

Find it very useful, and better than the 'Quest' that I had before.
It would be nice if you could program the unit alone, instead of via PC, but thats a personal preference.
The touch screen is great, as is the degree of detail you want, and if you get stuck in traffic, you can sometimes find a way round the hold-up by decreasing the area, and seeing any alternative route. This alas does not apply to motorways, but thats a problem that you'll never resolve!
I don't know if the other Garmin units are better than the 320 .
Have always had excellent assistance from customer service, and would happily buy another Garmin unit.