Thank you for your prompt reply. I ejected Garmin and the SD, closed Express and reconnected it all - you are correct, it restarted back to where it left off, but still stuck on 547 (after 20 mins).
My 4GB SD has only 760MB left available - could this be the problem. If I eject it, reformat and then reconnect will Express start from scratch, so that I can choose a smaller map coverage instead of Full Europe (as I can see no way of changing that option whilst it is stuck on 547)
MIKERGEE: It sounds like you may be on a older version of Garmin Express. At the time of this reply, version 3.2.18.0 is the latest. Please visit http://garmin.com/express to download the current version.