I did Access to HE but it was in science rather than medicine. It is certainly possible to get full distinctions for all units but it requires dedication and commitment. This is helped considerably if the group as a whole or several people in it are similarly motivated- group up with them and their enthusiasm will shine on you. If the teaching staff know this they will also be inclined to push you harder than they otherwise might. One of our teachers formerly worked in an NHS pathology laboratory and the so the course was orientated in such a way that we could create assignments based on subjects that fitted with our intended area of study. For example, for a physics unit I created a very detailed presentation on brachytherapy.
I treated the Access course as if it was University itself: every piece of work was prepared, written and referenced to a standard that would have been acceptable in any undergraduate degree program. It is an excellent way to prepare for the demands of any degree and completing it will give you a great confidence boost in the years ahead. I recall that Bristol had very stiff entry requirements in terms of grades from the Access course so you need to be pretty dedicated from day 1 of the course.
If you live in or near Bristol and intend to study medicine I strongly suggest you apply for the Pathways to health sciences (formerly access to Bristol) which is aimed at people living in the region who wish to study med/dent/vet. If you have been working in the RUH (which is an ace hospital btw) the pathways team will definitely look carefully at your application.
Keep up the focus, keep doing some healthcare shifts and if you need any other help by all means PM me as I have done exactly what you are intending to do.