Garmin 250W is the one we bought, only £130 and it does an excellent job.

There's an option for avoiding main roads, and I've found some fascinating routes using it. And the lady in the box is good company too. We call her Svetlana, which is an anagram of Le SatNav.

The great thing is the you don't have to do what she says - go the wrong way and she instantaneously recalculates and adjust the routes accordingly. She never gets cross about it either, unlike human navigators in a similar situation.

I'm looking forward to the version a few years down the road which will take over driving the car, and I can sit in the back and have a drink...