As long as you're prepared to accept a lower spec'd sat nav unit, then they're excellent. As a camera locator alone, they're worth the money - think of it as a RA Compact with a much larger colour screen. That said, the sat nav's a bit of a let down. Still full post code and address search, but mapping's not too clear and they're not as reliable as a Garmin or a Tom Tom.
That said, they're just under £170 at Halfords which means you can probably pick them up for about 150 on the web.
If you want both, the Garmin units are excellent sat nav's and they can take a (free) speed camera database from pocketgpsworld.com very easily. Despite it being free, it's very impressive - I use an Origin B2 (
http://www.originb2.com ) camera locator and I was still impressed with it.
