I've just got my hands on a really cute little GPS system called the Garmin StreetPilor i3. It's tiny, around the size of a tennis ball, but does all you would expect from an in-car navigation system. Give it a postcode and off you go. It works really well, successfully navigating us around Wales last weekend, and even has maps for the Isle of Man. Much recommended.

Here's the specs:
  • WAAS-enabled, 12 parallel channel GPS patch antenna with MCX-type connector for optional external antenna
  • Unit dimensions: 3.00” W x 2.74” H x 2.15” D
  • StreetPilot i3 display: 1.7” W x 1.3” H, 220 x 176 pixels, 32k-color sunlight-readable TFT with backlight
  • Weighs only 5.3 oz. (without batteries; includes vehicle suction cup mount)
  • Audible and visual navigation instructions and warnings
  • Includes 128MB TransFlash card for loading detailed maps
  • Features scroll wheel with click-to-enter, making it quick & easy to navigate
  • Offers a three dimensional mapping perspective, or 2-D overhead view
  • Battery life: up to 6 hours typical use on two AA batteries (7 hours maximum)
  • Includes removable 12-volt power adapter cable for external power while in your vehicle
  • Includes a vehicle suction cup mount which allows for easy adjustment and quick release
  • USB Interface
btw, Argos is selling these for around £99, but last I checked they were out of stock.

Garmin: StreetPilot i3