When you do an access course, you earn credits.
Most access courses do about 72 credits minimum.
15 of these are level 2, which you do at the beginning of the year usually.
The others are level 3, which is equivalent to A-Levels, BTEC, etc.
You do assignments every week (I usually do about 3-4 assignments weekly). Your grades for these assignments (Fail, Pass, Merit or Distinction) are what decide your grade for one credit.
You need 45 level 3 credits to pass the course, individual universities will ask for special grades for these. For etc. Some universities want you to have 15 Distinctions, the rest merits, etc.
If you already have your english and maths GCSE at grade C or above, you automatically get 6 extra level 2 credits
. You won't have to re-do these, if you don't, you'll need to take these alongside your course.
Hope this helps
. Don't follow any ucas point system, there is no equivalent. Just follow the credit system - It's tough at first but you get used to it