Best one i have seen for sub £200 is the tom tom one. I think this comes with an SD card whcoh would allow you to upgrade the maps (someone may be able to confirm?).

I used one last week for a day and thought it pretty neat, nice and slim and fits in top pocket. Would reroute quite quickly and was generaly very easy to use.

I am holding out until Jan/Feb and looking to buy a 710 or a 910, am hoping that these will drop closer to £200-£250 by then....hopefully.