Hi,
I've just completed the first year of my Occupational Therapy B.Sc. at Brunel and made it into the second year (phew!). I wouldn't worry about not being challenged by the course, it's academically very challenging and Placements 2, 3 and 4 are supposed to be physically quite tough as well.
I am a mature student and I had to do an Access to Healthcare course to be accepted onto the degree. The Access course was very demanding but was excellent preparation. I'm sure the O.T. degrees at other universities are equally as demanding, they all have to meet the same standard.
If you get CCC then i'm sure you'll be O.K. but expect to have to work damn hard when you reach uni. If you get As or Bs then you'll probably do just fine. The workload during the first year of the degree was immense, the first term in particular being a baptism of fire. Quite a few of my fellow students failed various assignments and/or exams and will have to redo them and resit exams in August to make it to second year. Quite a few of them are not expected to return next year. From last year, I learned that around 50 out of 120 students did not make it into second year.
That should give you an idea of the demands of the course. It's demanding because they have to cram so much into 3 years and also because you have to achieve a certain standard of competency before you can register and practice.