The drop out rate can vary from 5-10%, I think. Some people drop out voluntarily because the course doesn't suit them, then often go off and join another course somewhere else.
Of the people who fail and are asked to leave (or resit the year), I've found a good majority to be the type who would try and get coursework/lab solutions from other people and do very little work themselves. If you're prepared to work then you should have no problem if you meet the entry requirements. If you're not prepared to work, you'll probably fail at least one year and often the whole degree.