The work is a big step up from A-level. Its not really that hard to get to grips with, but there's so much of it!!
Personally I found A Levels very easy, so modular, so little to learn each time. It was great. Also my teachers were great and my classes small.
When you get to uni you could well be taught in lectures of 250 people and I certainly got the feeling that I shouldnt ask too many questions incase they were stupid or I could easily work them out from a book, so I didnt.
Its constant work, but if its in an area you enjoy than its great! personally I love all my modules here, even those im not so keen on its usually because theyres so much of it or its a bit harder to get to grips with (ive got a mental block on action potentials, still!) rather than because its boring.
I'm looking forward to the clinical years, they should be great.
Go for it!