Neil,
I was surfing the Costco website tonight and ran across a great deal on Tom Tom GPS units there. $129 on the One125 3.5" unit with a free dashboard beanbag mount. I haven't seen many basic GPS units from reputable companies at a price this good!
Here's the link from their website:
Costco - TomTom ONE125 3.5" Touchscreen w/ Bonus Dash Mount