I had the TomTom300 and it was really great, so easy to use. The only thing was, to get from Hanger Lane to M25/M4 interchange, it recommended going down the A406 and taking the M4, when obviously a better route is the A40/M25. Also, it doesn't work in the City because of all the tall buildings.
I only sold it because I memorised all the roads in London, Surrey, & Oxfordshire, thus rendering the unit useless for me. In conclusion, highly recommended.
I find tall buildings only block the signal for a few moments but the map stays on screen.
Good value unit IMO, if you do a lot of travelling to obscure casinos
