Have you been able to load the whole of Europe (top option) to your computer in one go? Whenever I tried it it kept on telling me that the zumo / SD card didn't have enough memory, without it letting me select the computer only option? Eventually did the western EU then the rest in two downloads onto the PC.
Here's how I do it for my Zumo 660 and Nuvi 765T (these have 4GB of internal memory, Zumo 550 users will have to use a subset of Europe that suits them best or make one of their own using Mapsource or MapInstall):
1/ Ensure that you have sufficient space on your SD card, 3GB or more should do the trick.
2/ Do the update (one off option rather than Lifetime updater is my preference) sending the mapping to the PC and SD card in the Zumo.
3/ Once complete delete the GMAP3D.IMG file from the Garmin folder on the Zumo's internal memory. This is the file containing data for the 3D buildings eye candy that, IMHO, is a worthless gimmick.
4/ Rename the 3 files (GMAPSUP1.GMA, GMAPSUP1.UNL, GMAPSUP1.IMG) on the SD card found in the Garmin folder to GMAPPROM.GMA, GMAPPROM.UNL, GMAPPROM.IMG.
5/ Check that the internal memory on your Zumo has anough room to fit these files onto with 100MB+ to spare for good measure. If there isn't enough room you'll need to delete some files; GMAPSUPP.IMG files are uploaded mapping data from Mapsource or MapInstall, move these to the Garmin folder of the SD card or delete them. Remove all except the voices you actually use from the Voices folder.
6/ Move the three files in 4 above to the Garmin folder.
Having left the Zumo and PC updating overnight the above took about 5 minutes to do with the exception of the transfer from SD card to internal memory which, once started, looked after itself.
My Zumo now has about 170MB of space free, there might not be enough room to it do this way in the next or subsequent update. Any supplementary mapping has to go onto the SD card.
This gives full European mapping with full junction view all on the internal memory in a format that you can't overwrite from Mapsource or MapInstall. It will lack 3D buildings where previously present but, IMHO, no great loss.