In most courses a fair proportion of students get 2:1s or above, so it should be attainable with hard work. It shouldn't be a cakewalk though.
To generalise any further on an individual basis is obviously impossible. An 'above average' student should get a 2:1, but then again how can you tell you're an above average student? A level performance isn't particularly relevant, so you start with a clean slate at the beginning of uni.