If you are still considering the pocket pc, the map of England will fit on a basic 128mb SD card. If you are looking for the European maps as well, I believe that the cheapest way of doing this would be to purchase a set with tomtom 3 and then upgrading to tomtom 5. This way you will get the european maps for free. If you do not want to change SD Cards between countries, you will need to purchase a 256mb SD card (not expensive) and this will give you coverage of all the major roads in europe. For coverage information, please go to:
http://www.tomtom.com/shop/upgrade.php?action=pdasub1
The added advantage that I've found using a pocket pc is that you can also use it for a diary, contacts (and with some models a mobile phone). I have not had the pleasure of using a tomtom go but on the other hand have not had any problems using the pocket pc.
Hope this helps you