If you are on vacation in the UK the Vodafone TopUp And Go offer is a great way to stay online without the tie-in of a contract. The Huawei USB dongle works great with Ubuntu (10.04). The only problem is that the network manager wizard configures the wrong APN for TopUp And Go. The correct APN is ppbundle.internet. After the wizard finished, go and change the properties in the connection like this (I use user web with password web, but this is maybe not necessary):

There is already a bug in launchpad that describes the problem.