Don't ignore the cheapest models
The most basic GPS untis make do with a 3.5'' (8.9 cm) screen and maps limited to a single country.
If they do offer live traffic information, then it's restricted to only the most important highways with little coverage of minor roads or town centres.
In any case, such systems aren't as helpful as the marketing would have you believe! Too many areas remain outside of the coverage area, and a lot of work remains to be done.
Despite lacking these systems, the cheapest sat navs are perfectly able to fulfil their primary function of getting you from A to B, as they're essentially based on the same software found in more advance models.
When it comes to the voice instructions your sat nav gives you, one feature to look out for is Text-to-Speech voice synthesis. While almost all GPS systems can give voice instructions like 'Turn right in 100 yards', they usually can't handle the names of streets and towns. Text-to-Speech allows them to give clear directions like 'Turn left onto Banbury Road', a much more natural way of getting round town.
On the subject of making these systems a little more realistic, that's partly the aim of TomTom's iQ Routes system. This suggests different routes depending on the time of day based on journey times measured in real life, not just the theoretical average speed on the roads you travel.
The nüvi 2595LMT is the fanciest model in Garmin's Advance series of mid-range sat navs. It has loads of functions, including all the navigation basics and an excellent voice recognition system. Plus, you can pick and choose optional web-based live services by connecting to an Android smartphone. What's more, the 2595LMT comes with lifetime map updates to keep you up to date but not out of pocket.
Best of the rest
Top Traffic Info
TomTom GO LIVE 825
This TomTom has a micro SD card slot and LIVE services (1 year free then £50 per year), as well as TomTom favourites like IQ Routes and Map Share. There are loads of points of interest, plus text-to-speech, Bluetooth and voice recognition.
Pocket Sat Nav
TomTom Navigator for iPhone
Why bother buying a stand-alone sat nav if your mobile already has a GPS chip? It's one less piece of equipment to carry, plus your phone fits neatly in your pocket for perfect portability.
Mio Spirit 485
With its big 4.3-inch screen and IQ Routes technology, this sat nav has all the basic functions occasional users will need to get from A to B. It's also very easy to use.
TomTom Start 60
With its 6-inch high-resolution screen, the TomTom Start 60 is certainly easy to read. Look out for TomTom's promotions offering Free lifetime maps on certain GPS models.
Garmin Zümo 350LM
Although we haven't got the full review online yet, our tests so far have shown the Garmin Zümo 300-series GPS to be a top choice for motorcycle riders. With Bluetooth, a 4.3" screen and lifetime maps, it has plenty to offer.