We us a Sportrak Pro and an Etrex yellow. The Sportrak keeps a lock under trees long after the Etrex has given and you get used to the overshoot problem. Reports are that the Explorists do not have that problem.
You can get UK topo maps for the Sportrak but not for any of the Garmin range. The maps are very useful, particularly for ensuring you're the right side of a river! I wouldn't buy a Garmin until maps are available.