For less than £320 you could get a HP Ipaq hw6915.
( Try a search on "pricerunner" or similar ).
This is a PDA with Wi-Fi, Bluetooth, and Infra Red.
The GPS receiver is built in - so no external aerials to flip out or plug in.
It IS a phone too - so you could get a PAYG SIM card and then you would be able to use the "Traffic" update feature too.
