Don't bother with one that detects laser, by the time it's done so, you'll have been caught. This is due to the way the laser guns work. They produce a very fine beam, very similar to a laser pen etc... For the little laser detector to see it, the laser would be shining right on it !
The Road Angel, Road Pilot, Origin B2 etc... are all very good units. If you were after sat nav as well (very useful and about the same price, if not cheaper than a stand alone GPS camera detector), go for a TomTom unit and you can download the free, constantly updated camera database from
www.pocketgps.co.uk This contains ALL the cameras around, including mobile, SPECS and Truvelo etc...
If not and you only want to get a stand alone GPS detector, go for one that is easily updated as, you're probably aware, the sites are always changing.
An added bonus of these GPS units is that you can see exactly how fast you're going ;o)