So I used a Uniden 3500Xlt which has Close Capture and a Radio Shack Pro-164 which has Signal Stalker. Both Close Capture and Signal Stalker do basically the same thing which is automatically tune into anyone or anything that transmits near you, allowing you to be aware of whats going on in a given area as well as anyone who is organised enough to use radios.

The antenna has a very, very strong magnetic base which did not move at all when I was driving at 70ish mph on the M25, it picks up everything from truck drivers and kids/builders with PMR446 radios to pirate radio stations on my way out of London.
When I got home I plugged my Uniden 3500Xlt into my laptop and use bctools to log when ever I transmitted on a cheap PMR446 handheld, I found that the antenna was good for a little over a 1 1/2 miles away from my house and it picked up my 2m and 70cm radios at well over 9 miles.
For £19.99 I don't think you can really go wrong with one, I'm very happy with its quality and it even worked okay below the 25-2000 MHz range listed on the box when I hooked it up to my little transceiver (only rx)