I did a science access course and it was a mixture of coursework and exams. There were some maths modules (6-12 credits) which were level 2 and all exam. The rest of the modules were level 3. Chemistry (18 credits) and physics (9 credits) were entirely exam based. Anatomy and physiology was mostly course work (12 credits) with one exam (3 credits). Study skills (9 credits), medical science (9 credits) and IT (6 credits) were coursework. There was also a chance to present a seminar paper to get credits.
I would say that exams on access courses can be harder to pass than coursework. To pass an access assignment you need to hit all the assessment criteria. If one assessment criterion is not met, then the assignment is failed. You can resit it, but it should be capped to a pass. Often in exams, there is only question for each criterion. Therefore, it is possible to fail with 99%. Coursework is easier because you have time to go over the assignment and ensure that each assessment criterion is met.
However, these exams are do-able. I managed to avoid any resubmissions, so it is possible. Also, IME coursework was more time consuming than revising for exams.