I have a Garmin Nuvii 300 which I bought last June and was very unhappy with, however I finally got the latest map updates which were released late 2006 and now find it excellent. The latest maps are City Navigator NT Europe v9 and are installed currently on all Garmin products. They claim almost 100% coverage of Ireland and UK and seems to be decent coverage for rest of Europe
PS the updates when the eventually were released were free, but think that was as my unit was still under warranty, normally update would have been US$75